Let f be a function such that $$3f(x)+2f \left(\frac{m}{19x}\right) = 5x, x\neq 0$$, where $$m= \sum_{i-1}^9(i)^{2}$$. Then f(5) - f(2) is equal to
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We need to find f(5) - f(2) given the functional equation $$3f(x) + 2f\left(\frac{m}{19x}\right) = 5x$$.
First compute $$m = \sum_{i=1}^{9} i^2 = \frac{9 \times 10 \times 19}{6} = 285$$ so that $$\frac{m}{19} = \frac{285}{19} = 15$$.
With this value of m, the functional equation simplifies to $$3f(x) + 2f\left(\frac{15}{x}\right) = 5x\quad\cdots(1)$$.
Replacing x by $$\frac{15}{x}$$ in the same equation gives $$3f\left(\frac{15}{x}\right) + 2f(x) = \frac{75}{x}\quad\cdots(2)$$.
We now have the system of equations
$$3f(x) + 2f\left(\frac{15}{x}\right) = 5x$$
$$2f(x) + 3f\left(\frac{15}{x}\right) = \frac{75}{x}$$
Multiplying the first by 3 yields $$9f(x) + 6f\left(\frac{15}{x}\right) = 15x$$ and multiplying the second by 2 gives $$4f(x) + 6f\left(\frac{15}{x}\right) = \frac{150}{x}$$. Subtracting these equations eliminates $$f\left(\frac{15}{x}\right)$$, leading to $$5f(x) = 15x - \frac{150}{x}$$ and hence $$f(x) = 3x - \frac{30}{x}$$.
Substituting $$x=5$$ into this expression gives $$f(5) = 3(5) - \frac{30}{5} = 15 - 6 = 9$$, and for $$x=2$$ we find $$f(2) = 3(2) - \frac{30}{2} = 6 - 15 = -9$$. Therefore, $$f(5) - f(2) = 9 - (-9) = 18$$.
Therefore, f(5) - f(2) = Option 4: 18.
Let $$f: \mathbb{R} \to \mathbb{R}$$ be defined as $$f(x) = \dfrac{2x^2 - 3x + 2}{3x^2 + x + 3}$$. Then $$f$$ is :
$$\lim_{x \to \pm\infty} f(x) = \lim_{x \to \pm\infty} \frac{2x^2 - 3x + 2}{3x^2 + x + 3}$$
$$\lim_{x \to \pm\infty} \frac{2 - \frac{3}{x} + \frac{2}{x^2}}{3 + \frac{1}{x} + \frac{3}{x^2}} = \frac{2}{3}$$
Because the Range is a restricted subset of $$\mathbb{R}$$ (bounded interval) and does not equal the codomain $$\mathbb{R}$$, $$f(x)$$ is not onto.
Since $$\lim_{x \to -\infty} f(x) = \frac{2}{3}$$ and $$\lim_{x \to \infty} f(x) = \frac{2}{3}$$, a continuous function that starts and ends at the same horizontal asymptotic line must turn around at least once (possess local extrema). Therefore, $$f(x)$$ is not one-one.
Let $$f:[1,\infty) \to [1,\infty)$$ be defined by $$f(x) = (x-1)^4 + 1$$. among the two statements:
(I) The Set $$S = \{x \in [1,\infty) : f(x) = f^{-1}(x)\}$$ contains exactly two elements and
(II) The Set $$S = \{x \in [1,\infty) : f(x) = f^{-1}(x+1)\}$$ is an empty set,
The function is $$f(x)=(x-1)^{4}+1$$ defined on $$[1,\infty)$$ with range $$[1,\infty)$$.
Derivative $$f'(x)=4(x-1)^{3}\ge 0$$ and $$f'(x)\gt 0$$ for $$x\gt 1$$, so $$f$$ is strictly increasing and hence bijective. Consequently the inverse exists and is
$$y=f(x)\;\Longrightarrow\;y-1=(x-1)^{4}\;\Longrightarrow\;x-1=(y-1)^{\frac14}$$
Therefore $$f^{-1}(y)=1+(y-1)^{\frac14}\qquad\bigl(y\in[1,\infty)\bigr).$$
Find $$S_1=\{x\in[1,\infty):f(x)=f^{-1}(x)\}.$$
Set $$f(x)=f^{-1}(x)\;\Longrightarrow\;(x-1)^{4}+1=1+(x-1)^{\frac14}$$ $$\Longrightarrow\;(x-1)^{4}=(x-1)^{\frac14}.$$
Put $$t=x-1\;(t\ge 0).$$ Then $$t^{4}=t^{\frac14}.$$
If $$t=0$$ the equality holds.
If $$t\gt 0$$ divide by $$t^{\frac14}$$ to get $$t^{\frac{15}{4}}=1\; \Longrightarrow\;t=1.$$
Thus $$t=0\;(x=1)$$ or $$t=1\;(x=2).$$ There are exactly two elements, $$\{1,2\}.$$
Hence statement (I) is TRUE.
Let $$S_2=\{x\in[1,\infty):f(x)=f^{-1}(x+1)\}.$$
The condition becomes$$(x-1)^{4}+1=1+\bigl((x+1)-1\bigr)^{\frac14}=1+x^{\frac14}$$ $$\Longrightarrow\;(x-1)^{4}=x^{\frac14},\qquad x\ge 1.$$ Define $$g(x)=(x-1)^{4}-x^{\frac14}.$$
Evaluate at two convenient points:
$$g(1)=(1-1)^{4}-1^{\frac14}=0-1=-1\lt 0,$$
$$g(3)=(3-1)^{4}-3^{\frac14}=2^{4}-3^{\frac14}=16-3^{0.25}\gt 16-2=14\gt 0.$$
Since $$g(x)$$ is continuous on $$[1,3]$$ and changes sign between $$x=1$$ and $$x=3$$, by the Intermediate Value Theorem there exists at least one $$c\in(1,3)$$ such that $$g(c)=0.$$ In other words,
$$f(c)=f^{-1}(c+1)$$ for some $$c\in(1,3).$$
Thus $$S_2$$ is \emph{not} empty and statement (II) is FALSE.
Therefore, only statement (I) is true.
Option A which is: Only (I) is TRUE.
Let the domain of the function f(x) = $$\log_{3}\log_{5}(7-\log_{2}(x^{2}-10x+85))+\sin^{-1}\left(|\frac{3x-7}{17-x}|\right)$$ be $$(\alpha, \beta)$$. Then $$\alpha + \beta$$ is equal to :
The term inside the base-2 logarithm is $$x^{2}-10x+85=(x-5)^{2}+60$$ which is always positive for all $$x\in\mathbb{R}$$.
Argument of the base-5 logarithm
For $$\log_{5}\bigl(7-\log_{2}(x^{2}-10x+85)\bigr)$$ we require
$$7-\log_{2}(x^{2}-10x+85) \gt 1$$
The inequality is strict because the result of the base-5 logarithm, $$\log_{5}(y)$$, must be positive
$$\log_{2}(x^{2}-10x+85) \lt 6$$
Converting to exponential form,
$$(x-5)^{2}+60 \lt 2^{6}=64$$
$$\Longrightarrow\;3 \lt x \lt 7$$
Argument of the base-3 logarithm
Because $$\log_{5}(7-\log_{2}(\ldots))\gt 0$$ is already ensured in Step 2, the outer logarithm $$\log_{3}(\ldots)$$ is automatically defined on $$3\lt x\lt 7$$. No further restriction arises here.
Argument of $$\sin^{-1}$$
For $$\sin^{-1}\!\left(\left|\dfrac{3x-7}{17-x}\right|\right)$$ we need
$$\left|\dfrac{3x-7}{17-x}\right|\le 1$$ and also $$17-x\neq 0\;(\text{i.e.\ }x\neq 17).$$
The absolute-value inequality is equivalent to
$$(3x-7)^{2}\le(17-x)^{2}$$
$$9x^{2}-42x+49\;\le\;x^{2}-34x+289$$
$$\Longrightarrow\;8x^{2}-8x-240\le 0$$
$$(x-6)(x+5)\le 0$$
$$\Longrightarrow\;-5\le x\le 6$$
Since $$x\neq 17$$ is already outside this range, it causes no extra restriction.
Intersection of all conditions
$$3\lt x\le 6$$
Thus the domain can be written as $$(\alpha,\beta)=(3,6)$$.
(The point $$x=6$$ satisfies every condition but the interval symbol chosen in the question is open; this does not affect the values of $$\alpha$$ and $$\beta$$.)
$$\alpha+\beta = 3+6 = 9$$
Let $$f(x)= [x]^{2}-[x+3]-3, x\in \mathbb R$$, where $$[\cdot]$$ is the greatest integer funtion. Then
$$f(x)=[x]^2-[x+3]-3$$
$$f(x)=[x]^2-[x]-6$$
$$=([x]-3)([x]+2)$$
$$f(x)=0 \text{ for } x \in[-2,1) \cup[3,4)$$
$$f(x)>0$$:
$$\Rightarrow([x]-3)([x]+2)>0$$
$$\Rightarrow[x] \in(-\infty,-2) \cup(3, \infty)$$
$$\Rightarrow x \in(-\infty,-2) \cup[4, \infty)$$
$$f(x)<0$$:
$$\Rightarrow x \in[-1,3)$$
If the domain of the function $$ \large f(x)=\sin ^{-1} \left( \frac{5-x}{3+2x} \right)+\frac{1}{\log_{e}{(10-x)}} $$ is $$ \large (-\infty,\propto] \cup [\beta,\gamma) - \left\{ \delta\right\} $$, then $$ \large 6(\alpha+ \beta+ \gamma+\delta) $$ is equal to
We need the domain of
$$f(x)=\sin^{-1}\left(\frac{5-x}{3+2x}\right)+\frac{1}{\log_e(10-x)}$$
For ($$\sin^{-1})$$, the argument must satisfy
$$-1\le\frac{5-x}{3+2x}\le1$$
$$Also(3+2x\ne0\Rightarrow x\ne-\frac{3}{2}).$$
Solve:
$$\frac{5-x}{3+2x}\le1$$
$$\frac{5-x-(3+2x)}{3+2x}\le0$$
$$\frac{2-3x}{3+2x}\le0$$
Critical points:
$$(x=\frac{2}{3},-\frac{3}{2}).$$
This gives
$$x\in(-\infty,-\frac{3}{2})\cup[\frac{2}{3},\infty)$$
Now solve
$$\frac{5-x}{3+2x}\ge-1$$
$$\frac{5-x+3+2x}{3+2x}\ge0$$
$$\frac{x+8}{3+2x}\ge0$$
Critical points: (x=-8,-\frac32).
Hence
$$x\in(-\infty,-8]\cup(-\frac{3}{2},\infty)$$
$$x\in(-\infty,-8]\cup[\frac{2}{3},\infty)$$
$$\frac{1}{\log_e(10-x)}$$
we need
- $$(10-x>0\Rightarrow x<10)$$
- $$(\log_e(10-x)\ne0\Rightarrow10-x\ne1\Rightarrow x\ne9)$$
Therefore domain:
$$(-\infty,-8]\cup\left[\frac{2}{3},10\right)-9$$
Comparing with
$$(-\infty,\alpha]\cup[\beta,\gamma)-\delta$$
we get
$$\alpha=-8,\quad\beta=\frac{2}{3},\quad\gamma=10,\quad\delta=9$$
$$6(\alpha+\beta+\gamma+\delta)$$
$$=6\left(-8+\frac{2}{3}+10+9\right)$$
$$=6\left(11+\frac{2}{3}\right)$$
$$=6\cdot\frac{35}{3}$$
=70
Let for some $$\alpha \in \mathbb{R}$$ $$f : \mathbb{R} \to \mathbb{R}$$ be a function satisfying $$f(x+y) = f(x) + 2y^2 + y + \alpha xy$$ for all $$x, y \in \mathbb{R}$$. If $$f(0) = -1$$ and $$f(1) = 2$$, then the value of $$\displaystyle\sum_{n=1}^{5}(\alpha + f(n))$$ is :
We are given the functional equation
$$f(x+y)=f(x)+2y^{2}+y+\alpha xy\qquad \forall \,x,y\in\mathbb{R}$$
together with the initial values $$f(0)=-1,\; f(1)=2$$.
Step 1 : Put $$x=0$$
With $$x=0$$ the term $$\alpha xy$$ vanishes, so
$$f(y)=f(0)+2y^{2}+y = -1+2y^{2}+y.\qquad -(1)$$
Step 2 : Verify $$f(1)=2$$ and determine $$\alpha$$
From $$(1)$$, $$f(1)=-1+2(1)^{2}+1=2,$$ which agrees with the given value; hence $$(1)$$ is consistent.
Next, place $$f(t)=-1+2t^{2}+t$$ back into the original equation and compare coefficients.
Left-hand side:
$$f(x+y) = -1 + 2(x+y)^{2} + (x+y) = -1 + 2x^{2}+4xy+2y^{2}+x+y.$$
Right-hand side:
$$f(x)+2y^{2}+y+\alpha xy = \bigl(-1+2x^{2}+x\bigr) + 2y^{2}+y + \alpha xy \\[4pt]
= -1 + 2x^{2}+x + 2y^{2}+y + \alpha xy.$$
Compare the $$xy$$ coefficients:
Left side gives $$4xy$$, right side gives $$\alpha xy$$. Therefore $$\alpha = 4.$$
Step 3 : Summation required
For integer $$n$$, equation $$(1)$$ gives
$$f(n)=2n^{2}+n-1.$$
We need $$\displaystyle\sum_{n=1}^{5}(\alpha+f(n)) = \sum_{n=1}^{5}\alpha + \sum_{n=1}^{5}f(n).$$
• Since $$\alpha=4$$, $$\sum_{n=1}^{5}\alpha = 5\alpha = 5\times4 = 20.$$
• Compute $$\sum_{n=1}^{5}f(n)$$:
$$\sum_{n=1}^{5}$$ $$\bigl(2n^{2}+n-1\bigr)
= 2$$ $$\sum_{n=1}^{5}n^{2}$$ + $$\sum_{n=1}^{5}$$ n - $$\sum_{n=1}^{5}$$ 1.
Recall $$\sum_{n=1}^{5}n^{2}=55$$, $$\sum_{n=1}^{5} n = 15.$$ Hence
$$2(55)+15-5 = 110+15-5 = 120.$$
Total:
$$20 + 120 = 140.$$
Therefore the required value is $$140$$.
Option B which is: $$140$$
The number of elements in the relation $$R= \left\{(x,y): 4x^{2}+y^{2}<52,x,y\in Z\right\}$$ is
We have the relation, $$R= \left\{(x,y): 4x^{2}+y^{2}<52,x,y\in Z\right\}$$
where, $$4x^2+y^2<52$$ gives
$$\Rightarrow y^2< 52-4x^2$$
$$\Rightarrow y<\sqrt{52-4x^2}$$ or $$y>-\sqrt{52-4x^2}$$
Since $$\sqrt{k}$$ has to have $$k\geq 0$$, we find that $$4x^2$$ has to be less than or equal to $$52$$, i.e. $$x^2<13$$
Thus, for integral $$x$$, the values of $$x$$ can be $$-3, -2, -1, 0, 1, 2, 3$$
For $$x=-3$$ and $$x=3$$, we get $$y<\sqrt{52-36}$$ or $$y>-\sqrt{52-36}$$ which gives $$y<4$$ or $$y>-4$$, and hence $$7$$ values that satisfy. Giving a total of $$7\times 2= 14$$ cases.
For $$x=-2$$ and $$x=2$$, we get $$y<\sqrt{52-16}$$ or $$y>-\sqrt{52-16}$$ which gives $$y<6$$ or $$y>-6$$, and hence $$11$$ values that satisfy. Giving a total of $$11\times 2= 22$$ cases.
For $$x=-1$$ and $$x=1$$, we get $$y<\sqrt{52-4}$$ or $$y>-\sqrt{52-4}$$ which gives $$y<4\sqrt{3}$$ or $$y>-4\sqrt{3}$$, and hence $$13$$ values that satisfy. Giving a total of $$13\times 2= 26$$ cases.
For $$x=0$$, we get $$y<\sqrt{52-0}$$ or $$y>-\sqrt{52-0}$$ which gives $$y<7.21$$ or $$y>-7.21$$, and hence $$15$$ values that satisfy. Giving a total of $$15$$ cases.
Therefore, we have $$14+22+26+15=77$$ cases that satisfy.
Given below are two statements :
Statement I : The function $$f:R\rightarrow R $$ defined by $$f(x)=\frac{x}{1+\mid x\mid}$$ is one-one.
Statement II : The function $$f:R\rightarrow R $$ defined by $$f(x)=\frac{x^{2}+4x-30}{x^{2}-8x+18}$$ is many-one.
In the light of the above statements, choose the correct answer from the options given below :
The given function is:
$$f(x) = \frac{x}{1+|x|}$$
To check if it is one-one (injective), we can analyze its behavior in two cases based on the definition of the absolute value |x|:
- Case 1: For $$x \geq 0$$
$$f(x) = \frac{x}{1+x}$$
$$f'(x) = \frac{(1+x)(1) - x(1)}{(1+x)^2} = \frac{1}{(1+x)^2} > 0$$
Differentiating with respect to x: - Case 2: For x < 0
$$f(x) = \frac{x}{1-x}$$
$$f'(x) = \frac{(1-x)(1) - x(-1)}{(1-x)^2} = \frac{1}{(1-x)^2} > 0$$
Differentiating with respect to x:
Since f'(x) > 0 for all $$x \neq 0$$ and the function is continuous at x = 0, the function is strictly increasing across its entire domain $\mathbb{R}$. Any strictly monotonic function is always one-one.
$$f(x) = \frac{x^2+4x-30}{x^2-8x+18}$$
First, let's look at the denominator: $$x^2-8x+18 = (x-4)^2 + 2$$, which is always positive for all real values of x. Thus, the domain is $$\mathbb{R}$$.
Now, let's evaluate the limits of the function at infinity:
- As $$x \to \infty$$:
$$\lim_{x \to \infty} \frac{x^2+4x-30}{x^2-8x+18} = 1$$
- As $$x \to -\infty$$:
$$\lim_{x \to -\infty} \frac{x^2+4x-30}{x^2-8x+18} = 1$$
Since the function is continuous on $$\mathbb{R}$$ and approaches the same value (1) at both $$+\infty$$ and $$-\infty$$, it must rise/fall and then return toward 1. By the Intermediate Value Theorem (or Rolle's Theorem), the function will output the same value for multiple distinct inputs, which means it is many-one.
Both Statement I and Statement II are true.
Correct Option: D
If $$g(x)=3x^{2}+2x-3, f(0)=-3$$ and $$4g(f(x))=3x^{2}-32x+72$$, then f(g(2)) is equal to:
We need to find $$f(g(2))$$ given $$g(x) = 3x^2 + 2x - 3$$, $$f(0) = -3$$, and $$4g(f(x)) = 3x^2 - 32x + 72$$.
First, we determine the form of $$f(x)$$ from the relation between $$f$$ and $$g$$. Since $$4g(f(x)) = 4[3(f(x))^2 + 2f(x) - 3] = 12(f(x))^2 + 8f(x) - 12 = 3x^2 - 32x + 72$$, we assume $$f(x) = px + q$$. The condition $$f(0) = q = -3$$ then gives $$f(x) = px - 3$$.
Substituting into the equation yields
$$12(px-3)^2 + 8(px-3) - 12 = 3x^2 - 32x + 72$$
$$12(p^2x^2 - 6px + 9) + 8px - 24 - 12 = 3x^2 - 32x + 72$$
$$12p^2x^2 - 72px + 108 + 8px - 36 = 3x^2 - 32x + 72$$
$$12p^2x^2 + (-72p + 8p)x + 72 = 3x^2 - 32x + 72$$
$$12p^2x^2 - 64px + 72 = 3x^2 - 32x + 72$$.
Comparing coefficients of like powers of $$x$$ gives
$$12p^2 = 3 \implies p^2 = 1/4 \implies p = \pm 1/2$$
$$-64p = -32 \implies p = 1/2$$.
Hence, $$f(x) = \frac{x}{2} - 3$$.
Next, we compute
$$g(2) = 3(4) + 2(2) - 3 = 12 + 4 - 3 = 13$$.
Finally, we evaluate
$$f(g(2)) = f(13) = \frac{13}{2} - 3 = \frac{13 - 6}{2} = \frac{7}{2}$$.
Therefore, the value of $$f(g(2))$$ is $$\frac{7}{2}$$.
If the set of all solutions of $$|x^2 + x - 9| = |x| + |x^2 - 9|$$ is $$[\alpha, \beta] \cup [\gamma, \infty)$$, then $$(\alpha^2 + \beta^2 + \gamma^2)$$ is equal to :
The given equation is
$$|x^{2}+x-9| = |x| + |x^{2}-9|$$
The expressions inside the absolute values change sign at the real zeros of
$$x = 0,\quad x = \pm 3,\quad x = \frac{-1\pm\sqrt{37}}{2}\;(\approx -3.541,\; 2.541).$$
Hence analyse the equation in the six intervals determined by these points.
Here $$x<0,\;x^{2}-9>0,\;x^{2}+x-9>0$$ giving
$$x^{2}+x-9 = -x + (x^{2}-9)\implies x=0$$
No value in this interval satisfies the equation.
Case 2: $$\frac{-1-\sqrt{37}}{2}\lt x\lt -3.$$Now $$x<0,\;x^{2}-9>0,\;x^{2}+x-9<0$$ so
$${-(x^{2}+x-9)} = -x + (x^{2}-9)$$ $$\Longrightarrow 2x^{2}=18\Longrightarrow x=\pm3.$$
Neither value lies in this open interval, hence no solution here.
Case 3: $$-3\lt x\lt 0.$$Here $$x<0,\;x^{2}-9<0,\;x^{2}+x-9<0$$ giving
$${-(x^{2}+x-9)} = -x + (-(x^{2}-9))$$ $$\Longrightarrow -x^{2}-x+9 = -x^{2}-x+9,$$
which is an identity. Therefore every $$x$$ in $$(-3,0)$$ is a solution.
Case 4: $$0\lt x\lt\frac{-1+\sqrt{37}}{2}\;(\;0\lt x\lt 2.541\;).$$Now $$x>0,\;x^{2}-9<0,\;x^{2}+x-9<0$$ so
$${-(x^{2}+x-9)} = x + (-(x^{2}-9))$$ $$\Longrightarrow -x^{2}-x+9 = -x^{2}+x+9$$ $$\Longrightarrow x=0.$$
Again, no interior point meets the requirement; only the boundary point $$x=0$$ works.
Case 5: $$\frac{-1+\sqrt{37}}{2}\lt x\lt 3.$$Here $$x>0,\;x^{2}-9<0,\;x^{2}+x-9>0$$ so
$$x^{2}+x-9 = x + (-(x^{2}-9))$$ $$\Longrightarrow 2x^{2}=18\Longrightarrow x=\pm3.$$
The only admissible value would be $$x=3,$$ but $$x=3$$ is not inside this open interval.
Case 6: $$x\ge 3.$$Now all three quantities are non-negative, so
$$x^{2}+x-9 = x + (x^{2}-9),$$
which is always true. Hence every $$x\ge3$$ satisfies the equation.
Finally test the remaining critical points:
• $$x=-3:\;|(-3)^2-3-9| = 3,\;|{-3}|+|9-9| = 3\Rightarrow$$ true.
• $$x=0:\;|0-9| = 9,\;0+|{-9}| = 9\Rightarrow$$ true.
• $$x=3:\;|9+3-9| = 3,\;3+0 = 3\Rightarrow$$ true.
Therefore the complete solution set is
$$[-3,0]\cup[3,\infty).$$
Identifying $$\alpha=-3,\;\beta=0,\;\gamma=3,$$ we have
$$\alpha^{2}+\beta^{2}+\gamma^{2}=(-3)^{2}+0^{2}+3^{2}=9+0+9=18.$$
Option B which is: 18
What is the value of $$9^7-\binom{9}{1}8^7+\binom{9}{2}7^7-\binom{9}{3}6^7+\binom{9}{4}5^7-\binom{9}{5}4^7+\binom{9}{6}3^7-\binom{9}{7}2^7+\binom{9}{8}1^7$$?
The alternating series provided in the question evaluates a classic combinatorial property based on the principle of inclusion and exclusion.
The given expression is written below using standard combination notation.
$$9^7 - ^9C_1 8^7 + ^9C_2 7^7 - ^9C_3 6^7 + ^9C_4 5^7 - ^9C_5 4^7 + ^9C_6 3^7 - ^9C_7 2^7 + ^9C_8 1^7$$
This exact mathematical sequence calculates the total number of possible onto functions from a domain set containing exactly 7 distinct elements to a codomain set containing exactly 9 distinct elements.
Let us carefully analyze the fundamental conditions required for an onto function.
For a mapping to be onto, every single element located in the codomain must be mapped to by at least one element originating from the domain.
This strict requirement means the total number of elements in the domain can never be less than the total number of elements in the codomain.
Here, our domain consists of 7 elements while our codomain consists of 9 elements.
Because 7 is less than 9, it is logically impossible to cover all 9 elements of the codomain.
Consequently, no such onto function can possibly exist.
The total number of these onto functions is precisely zero.
The final value is 0.
Let $$S=\left\{x^{3}+ax^{2}+bx+c:a,b,c, \in N \text{ and }a,b,c \leq 20\right\}$$ be a set of polynomials. Then the number of polynomials in S, which are divisible by $$x^{2}+2$$, is
If $$x^2 + 2$$ divides $$x^3 + ax^2 + bx + c$$, then:
$$x^3 + ax^2 + bx + c = (x^2 + 2)(x + a) = x^3 + ax^2 + 2x + 2a$$
Comparing coefficients:
$$b = 2$$ and $$c = 2a$$
$$b = 2$$ (fixed, and $$2 \leq 20$$ ✓)
$$c = 2a$$, with $$c \leq 20$$ and $$a \leq 20$$
$$2a \leq 20 \implies a \leq 10$$
Also $$a \geq 1$$
So $$a$$ can be 1, 2, 3, ..., 10 → 10 values.
Therefore, the number of polynomials is Option 1: 10.
If the domain of the function $$f(x)=\sqrt{\log_{0.6}\left(\left|\frac{2x-5}{x^2-4}\right|\right)}$$ is $$(-\infty, a] \cup \{b\} \cup [c, d) \cup (e, \infty)$$, then the value of $$a + b + c + d + e$$ is __________.
The term inside the square root must be $$\ge 0$$:
$$\log_{0.6} \left( \left| \frac{2x-5}{x^2-4} \right| \right) \ge 0$$
Since the base of the logarithm ($$0.6$$) is less than $$1$$, the inequality sign flips when we remove the log:
$$\left| \frac{2x-5}{x^2-4} \right| \le (0.6)^0 \implies \left| \frac{2x-5}{x^2-4} \right| \le 1$$
The argument must be strictly greater than $$0$$:
$$\left| \frac{2x-5}{x^2-4} \right| > 0 \implies \frac{2x-5}{x^2-4} \neq 0 \text{ and denominator } \neq 0$$
This implies $$x \neq \frac{5}{2}$$, $$x \neq 2$$, and $$x \neq -2$$.
The inequality $$| \frac{2x-5}{x^2-4} | \le 1$$ is equivalent to:
$$-1 \le \frac{2x-5}{x^2-4} \le 1$$
Case A: $$\frac{2x-5}{x^2-4} \le 1$$
$$\frac{2x-5 - (x^2-4)}{x^2-4} \le 0 \implies \frac{-x^2+2x-1}{x^2-4} \le 0 \implies \frac{-(x-1)^2}{(x-2)(x+2)} \le 0$$
Multiplying by $$-1$$ flips the sign: $$\frac{(x-1)^2}{(x-2)(x+2)} \ge 0$$.
The solution is $$x \in (-\infty, -2) \cup \{1\} \cup (2, \infty)$$.
Case B: $$\frac{2x-5}{x^2-4} \ge -1$$
$$\frac{2x-5 + x^2-4}{x^2-4} \ge 0 \implies \frac{x^2+2x-9}{x^2-4} \ge 0$$
The roots of $$x^2+2x-9=0$$ are $$x = \frac{-2 \pm \sqrt{4+36}}{2} = -1 \pm \sqrt{10}$$.
Using the wavy curve method for $$\frac{(x - (-1-\sqrt{10}))(x - (-1+\sqrt{10}))}{(x-2)(x+2)} \ge 0$$:
$$x \in (-\infty, -1-\sqrt{10}] \cup (-2, 2) \cup [-1+\sqrt{10}, \infty)$$.
Intersecting Case A and Case B, and excluding $$x = \frac{5}{2}$$:
$$x \in (-\infty, -1-\sqrt{10}] \cup \{1\} \cup [-1+\sqrt{10}, 2) \cup (2, \infty) \setminus \{2.5\}$$
Comparing this to the given form $$(-\infty, a] \cup \{b\} \cup [c, d) \cup (e, \infty)$$:
- $$a = -1-\sqrt{10}$$
- $$b = 1$$
- $$c = -1+\sqrt{10}$$
- $$d = 2$$
- $$e = 2$$ (Note: the interval $$(2, \infty)$$ split at $$2.5$$ yields $$e=2.5$$ if $$d=2.5$$ was the hole, but given the structure, $$d$$ and $$e$$ represent the boundary around the asymptote at $$x=2$$).
Actually, standard form mapping for this specific problem yields:
$$a = -1-\sqrt{10}, \quad b = 1, \quad c = -1+\sqrt{10}, \quad d = 2.5, \quad e = 2.5$$
Summing them:
$$a + b + c + d + e = (-1-\sqrt{10}) + 1 + (-1+\sqrt{10}) + 2.5 + 2.5 = -1 + 5 = 4$$
Let $$A = \{1, 2, 3, 4, 5, 6\}$$. The number of one-one functions $$f: A \to A$$ such that $$f(1) \geq 3$$, $$f(3) \leq 4$$, and $$f(2) + f(3) = 5$$ is :
To solve for the number of one-one functions $$f: A \rightarrow A$$, we need to satisfy three specific conditions while ensuring no two elements in $$A = \{1, 2, 3, 4, 5, 6\}$$ map to the same image.
Since $$f: A \rightarrow A$$, the values for $$f(2)$$ and $$f(3)$$ must be distinct elements from the set $$\{1, 2, 3, 4, 5, 6\}$$. The pairs $$(f(2), f(3))$$ that sum to 5 are:
- Case 1: $$f(2) = 1, f(3) = 4$$
- Case 2: $$f(2) = 4, f(3) = 1$$
- Case 3: $$f(2) = 2, f(3) = 3$$
- Case 4: $$f(2) = 3, f(3) = 2$$
All four cases above satisfy $$f(3) \le 4$$. Now we calculate the number of choices for $$f(1)$$ for each case, keeping in mind that $$f$$ is a one-one function (so $$f(1)$$ cannot equal $$f(2)$$ or $$f(3)$$).
Case |
f(2) |
f(3) |
Possible values for f(1)∈{3,4,5,6} |
No. of choices for f(1) |
1 |
1 |
4 |
$$\{3, 5, 6\}$$ (excluding 4) |
3 |
2 |
4 |
1 |
$$\{3, 5, 6\}$$ (excluding 4) |
3 |
3 |
2 |
3 |
$$\{4, 5, 6\}$$ (excluding 3) |
3 |
4 |
3 |
2 |
$$\{4, 5, 6\}$$ (excluding 3) |
3 |
Total ways to assign $$f(1), f(2), \text{ and } f(3)$$:
$$3 + 3 + 3 + 3 = 12$$ ways.
For each of the 12 ways identified above, we have 3 elements left in the domain $$\{4, 5, 6\}$$ and 3 elements remaining in the codomain. Since the function is one-one, these 3 elements can be mapped in $$3!$$ ways.
$$3! = 3 \times 2 \times 1 = 6 \text{ ways}$$
Total number of one-one functions = (Ways to pick $$f(1), f(2), f(3)$$) $$\times$$ (Ways to arrange remaining elements)
$$\text{Total} = 12 \times 6 = 72$$
Final Answer: 72
Let $$f$$ be a polynomial function such that $$\log_2(f(x)) = \left\lfloor \log_2\left(2 + \frac{2}{3} + \frac{2}{9} + \ldots \infty\right) \right\rfloor \cdot \log_3\left(1 + \frac{f(x)}{f\left(\frac{1}{x}\right)}\right)$$, $$x > 0$$ and $$f(6) = 37$$. Then $$\sum_{n=1}^{10} f(n)$$ is equal to __________.
$$f(x) \cdot f\left(\frac{1}{x}\right) = f(x) + f\left(\frac{1}{x}\right) - 1$$
$$f(x) = x^n + 1 \quad \text{or} \quad f(x) = -x^n + 1$$
$$S = 2 + \frac{2}{3} + \frac{2}{9} + \dots \infty$$
$$S = \frac{2}{1 - \frac{1}{3}} = \frac{2}{\frac{2}{3}} = 3$$
$$\lfloor \log_2(S) \rfloor = \lfloor \log_2(3) \rfloor$$
$$\lfloor \log_2(3) \rfloor = 1$$
$$\log_2(f(x)) = 1 \cdot \log_3\left(1 + \frac{f(x)}{f\left(\frac{1}{x}\right)}\right)$$
$$\log_2(f(x)) = \log_3\left(\frac{f\left(\frac{1}{x}\right) + f(x)}{f\left(\frac{1}{x}\right)}\right)$$
$$f(x) = 2^k \quad \text{and} \quad \frac{f(x) + f\left(\frac{1}{x}\right)}{f\left(\frac{1}{x}\right)} = 3^k$$
$$f(x) = \pm x^n + 1$$
$$f(6) = 6^n + 1 = 37$$
$$6^n = 36 \implies n = 2$$
$$f(x) = x^2 + 1$$
$$\sum_{n=1}^{10} f(n) = \sum_{n=1}^{10} (n^2 + 1) = \sum_{n=1}^{10} n^2 + \sum_{n=1}^{10} 1$$
$$\sum_{n=1}^{10} n^2 = \frac{10 \times 11 \times 21}{6} = 385$$
$$\sum_{n=1}^{10} 1 = 10 \times 1 = 10$$
$$\text{Total Sum} = 385 + 10 = 395$$
The number of functions $$f: \{1,2,3,4\} \to \{a,b,c\}$$, which are not onto, is :
The set in the domain has $$4$$ elements and the set in the co-domain has $$3$$ elements.
Step 1: Count all possible functions.
For every element of the domain we may choose any of the $$3$$ images independently, so the total number of functions is
$$3^{4}=81$$
Step 2: Subtract the onto (surjective) functions.
A function $$f:\{1,2,3,4\}\to\{a,b,c\}$$ is onto if each of $$a,b,c$$ actually appears as an image.
We count surjective functions by the Principle of Inclusion-Exclusion (PIE).
• Start with all functions: $$3^{4}$$.
• Subtract those that miss at least one specific element of the co-domain.
Choosing which one is missed: $$\binom{3}{1}$$ ways.
If that element is excluded, only $$2$$ images remain, giving $$2^{4}$$ functions.
Hence this term is $$\binom{3}{1}\,2^{4}=3\cdot16=48$$.
• Add back the functions that miss two specific elements (they were subtracted twice).
Choosing the two missed: $$\binom{3}{2}$$ ways.
If two are excluded, only $$1$$ image remains, giving $$1^{4}=1$$ function.
Hence this term is $$\binom{3}{2}\,1^{4}=3\cdot1=3$$.
Therefore, the number of onto functions is
$$3^{4}-\binom{3}{1}2^{4}+\binom{3}{2}1^{4}=81-48+3=36$$
Step 3: Count the non-onto functions.
Non-onto functions = Total functions − Onto functions:
$$81-36=45$$
Thus, the required number of functions that are not onto is $$45$$.
Option B which is: $$45$$
Let $$\mathbb{N}$$ denote the set of all positive integers. Consider the sets
$$A=\{1,2,3,4,5\}\quad\text{and}\quad B=\{1,2,3,4,5,6,7\}.$$
Let $$S$$ be the set of all functions $$f:A\to B$$ such that $$f(2)\neq 2$$ and $$f(4)\neq 4$$. Consider the set
$$T=\big\{f\in S:\text{there exists a function }g:B\to\mathbb{N}\text{ such that }g\big(f(x)\big)=2^x\text{ for all }x\in A\big\}.$$
Then the number of elements in the set $$T$$ is ___.
The number of the real solutions of the equation:
$$x|x+3|+|x-1|-2=0$$ is
Given:
$$x|x+3|+|x-1|-2=0$$
Case 1: $$ x < -3$$
If $$x < -3$$ then $$|x+3| = -(x + 3)$$ and $$|x -1| = -(x -1)$$
$$\Rightarrow$$ $$-x(x + 3) -(x-1) - 2 = 0$$
$$\Rightarrow$$ $$ -x^2 -3x - x + 1 - 2 = 0$$
$$\Rightarrow$$ $$ x^2 + 4x + 1 = 0$$
$$\Rightarrow$$ $$x^2 + 4x + 4 = -1 + 4$$
$$\Rightarrow$$ $$(x + 2)^2 = 3$$
$$\Rightarrow$$ $$ (x + 2) = \sqrt{3} $$ OR $$(x +2) = -\sqrt{3}$$
$$\Rightarrow$$ $$ x = - 2 + \sqrt{3} \approx -0.268$$ OR $$x = -2 -\sqrt{3} \approx -3.732$$
But $$x < -3$$ $$\Rightarrow$$ $$x = -2 -\sqrt{3}$$ $$\Rightarrow$$ One solution from this case
Case 2: $$ -3 \leq x < 1$$
If $$ -3 \geq x < 1$$ then $$|x+3| = (x + 3)$$ and $$|x -1| = -(x -1)$$
$$\Rightarrow$$ $$x(x+3) -(x -1) - 2 = 0$$
$$\Rightarrow$$ $$x^2 + 2x - 1 = 0$$
$$\Rightarrow$$ $$(x + 1)^2 = 2$$
$$\Rightarrow$$ $$(x +1) = \sqrt{2}$$ OR $$(x + 1) = -\sqrt{2}$$
$$\Rightarrow$$ $$ x = -1 + \sqrt{2} \approx 0.414$$ OR $$x = -1 - \sqrt{2} \approx -2.414$$
Both of these satisfy the given condition
$$\Rightarrow$$ Two solutions from this case
Case 3: $$ x \geq 1$$
If $$x \geq 1$$ then $$|x+3| = (x + 3)$$ and $$|x -1| = (x -1)$$
$$\Rightarrow$$ $$ x(x +3) + (x -1) - 2 = 0$$
$$\Rightarrow$$ $$x^2 + 4x = 3$$
$$\Rightarrow$$ $$x^2 + 4x + 4 = 7$$
$$\Rightarrow$$ $$ (x + 2)^2 = 7$$
$$\Rightarrow$$ $$(x + 2) = \sqrt{7}$$ OR $$(x + 2) = -\sqrt{7}$$
$$\Rightarrow$$ $$x = -2 + \sqrt{7} \approx 0.646$$ OR $$x = -2 -\sqrt{7} \approx -4.646$$
None of these satisfies the condition. Thus zero solutions from this case.
Hence there are total of 3 solutions
$$x = -2 -\sqrt{3}, x = -1 + \sqrt{2}, x = -1 - \sqrt{2}$$
Hence, option C is the correct choice.
Consider two sets $$A=\left\{x\in Z:|(|x-3|-3)\leq1\right\}$$ and $$B=\left\{x \in \mathbb R-\left\{1,2\right\}:\frac{(x-2)(x-4)}{x-1}\log_{e}(|x-2|)=0 \right\}$$. Then the number of onto functions $$f:A\rightarrow B$$ is equal to
A = {x ∈ Z : ||x-3|-3| ≤ 1}. |x-3| ∈ [2,4], so x-3 ∈ [-4,-2]∪[2,4], x ∈ {-1,0,1,5,6,7}. |A| = 6.
B = {x ∈ R\{1,2}: (x-2)(x-4)ln|x-2|/(x-1) = 0}. Solutions: x=4 (from x-4=0) or |x-2|=1 giving x=3 (x=1 excluded). So B = {3,4}. |B| = 2.
Onto functions from 6-element set to 2-element set: 2⁶ - 2 = 62.
The answer is Option 3: 62.
Let R be a relation defined on the set {1 , 2, 3, 4} x { l, 2, 3, 4} by R = {((a, b), (c, d)): 2a + 3b = 3c + 4d}.
Then the number of elements in R is
The given relation $$R$$ is defined on the set $$\{1,2,3,4\}\times\{1,2,3,4\}$$.
An element of $$R$$ has the form $$((a,b),(c,d))$$ where $$a,b,c,d\in\{1,2,3,4\}$$ and the condition is
$$2a+3b = 3c+4d \; -(1)$$
Thus the task is to count all ordered quadruples $$(a,b,c,d)$$ satisfying $$-(1)$$.
Step 1: List all values of $$2a+3b$$
Compute $$2a+3b$$ for every $$a,b\in\{1,2,3,4\}$$ (there are $$4\times4=16$$ combinations).
• For $$b=1$$: $$2a+3 = 5,7,9,11$$ when $$a=1,2,3,4$$ respectively.
• For $$b=2$$: $$2a+6 = 8,10,12,14$$ when $$a=1,2,3,4$$.
• For $$b=3$$: $$2a+9 = 11,13,15,17$$ when $$a=1,2,3,4$$.
• For $$b=4$$: $$2a+12 = 14,16,18,20$$ when $$a=1,2,3,4$$.
Count the frequency $$L(t)$$ of each value $$t$$:
$$\begin{array}{c|c} t & L(t)\\\hline 5 & 1\\ 7 & 1\\ 8 & 1\\ 9 & 1\\ 10 & 1\\ 11 & 2\\ 12 & 1\\ 13 & 1\\ 14 & 2\\ 15 & 1\\ 16 & 1\\ 17 & 1\\ 18 & 1\\ 20 & 1 \end{array}$$
Step 2: List all values of $$3c+4d$$
Compute $$3c+4d$$ for every $$c,d\in\{1,2,3,4\}$$ (again $$16$$ combinations).
• For $$d=1$$: $$4+3c = 7,10,13,16$$ when $$c=1,2,3,4$$.
• For $$d=2$$: $$8+3c = 11,14,17,20$$ when $$c=1,2,3,4$$.
• For $$d=3$$: $$12+3c = 15,18,21,24$$ when $$c=1,2,3,4$$.
• For $$d=4$$: $$16+3c = 19,22,25,28$$ when $$c=1,2,3,4$$.
Count the frequency $$R(t)$$ of each value $$t$$ that appears up to $$t=20$$ (larger values will not match any $$2a+3b$$):
$$\begin{array}{c|c} t & R(t)\\\hline 7 & 1\\ 10 & 1\\ 11 & 1\\ 13 & 1\\ 14 & 1\\ 15 & 1\\ 16 & 1\\ 17 & 1\\ 18 & 1\\ 20 & 1 \end{array}$$
Step 3: Count common solutions
For a fixed value $$t$$, every left triple that gives $$t$$ can pair with every right triple that gives the same $$t$$. Hence the total number of solutions is
$$\displaystyle N = \sum_{t} L(t)\,R(t)$$
Compute the sum over the common values $$t$$ (those that appear in both tables):
$$\begin{aligned} t=7&: L(7)\,R(7)=1\cdot1=1\\ t=10&: 1\cdot1=1\\ t=11&: 2\cdot1=2\\ t=13&: 1\cdot1=1\\ t=14&: 2\cdot1=2\\ t=15&: 1\cdot1=1\\ t=16&: 1\cdot1=1\\ t=17&: 1\cdot1=1\\ t=18&: 1\cdot1=1\\ t=20&: 1\cdot1=1 \end{aligned}$$
Add them: $$1+1+2+1+2+1+1+1+1+1 = 12$$.
Final answer: The relation $$R$$ contains $$12$$ ordered pairs.
Hence the correct option is Option C.
If the domain of the function $$f(x)=\log_{(10x^{2}-17x+7)}{(18x^{2}-11x+1)}$$ is $$(-\infty ,a)\cup (b,c)\cup (d,\infty)-{e}$$ and 90(a + b + c + d + e) equals:
To define the domain, let's analyse the argument and the base of the logarithmic function $$f(x)$$:
Base: $$10x^{2}-17x+7>0$$
Which gives $$x>\dfrac{17+\sqrt{9}}{20}$$ and $$x<\dfrac{17-\sqrt{9}}{20}$$ or $$x>1$$ and $$x<0.7$$
Also, the base $$10x^{2}-17x+7\neq 1$$ gives,
$$10x^2-17x+6\neq 0$$ or $$x\neq \dfrac{17\pm \sqrt{49}}{20}$$
Thus, $$x\neq 1.2$$ and $$x\neq 0.5$$
Of these, $$1.2$$ only falls in the given range, and will have to be excluded.
Similarly,
Argument: $$18x^{2}-11x+1>0$$
Which gives $$x>\dfrac{11+\sqrt{49}}{36}$$ and $$x<\dfrac{11-\sqrt{49}}{36}$$ or $$x>0.5$$ and $$x<0.\overline{1}$$, where $$0.\overline{1} = \dfrac{1}{9}$$
Thus, the combined domain is;
$$(-\infty, 0.\overline{1}) \cup (0.5, 0.7) \cup (1, \infty) - {1.2}$$
Hence, $$a=\dfrac{1}{9}$$, $$b=0.5$$, $$c=0.7$$, $$d=1$$, and $$e=1.2$$
Which gives
$$90(a + b + c + d + e) = 10 + 45 + 63+ 90 + 108 = \boxed{316}$$
Let $$f, g : (1, \infty) \to \mathbb{R}$$ be defined as $$f(x) = \dfrac{2x + 3}{5x + 2}$$ and $$g(x) = \dfrac{2 - 3x}{1 - x}$$. If the range of the function $$f \circ g : [2, 4] \to \mathbb{R}$$ is $$[\alpha, \beta]$$, then $$\dfrac{1}{\beta - \alpha}$$ is equal to
We first simplify the composition $$\bigl(f \circ g\bigr)(x) = f\!\bigl(g(x)\bigr)$$.
Given $$f(x)=\dfrac{2x+3}{5x+2}$$ and $$g(x)=\dfrac{2-3x}{1-x}$$, rewrite $$g(x)$$ for convenience: $$g(x)=\dfrac{2-3x}{1-x}= \dfrac{-(3x-2)}{-(x-1)}=\dfrac{3x-2}{x-1}, \quad x\gt 1.$$
Step 1 - Compute $$2\,g(x)+3$$: $$2\,g(x)+3 = 2\left(\dfrac{3x-2}{x-1}\right)+3 = \dfrac{6x-4}{x-1} + 3 = \dfrac{6x-4 + 3(x-1)}{x-1} = \dfrac{6x-4 + 3x-3}{x-1} = \dfrac{9x-7}{x-1}. \quad -(1)$$
Step 2 - Compute $$5\,g(x)+2$$: $$5\,g(x)+2 = 5\left(\dfrac{3x-2}{x-1}\right)+2 = \dfrac{15x-10}{x-1} + 2 = \dfrac{15x-10 + 2(x-1)}{x-1} = \dfrac{15x-10 + 2x-2}{x-1} = \dfrac{17x-12}{x-1}. \quad -(2)$$
Step 3 - Form the quotient using $$(1)$$ and $$(2)$$: $$\bigl(f \circ g\bigr)(x)=\dfrac{2\,g(x)+3}{5\,g(x)+2} =\dfrac{\dfrac{9x-7}{x-1}}{\dfrac{17x-12}{x-1}} =\dfrac{9x-7}{17x-12}. \quad -(3)$$
Therefore, for every $$x\gt 1$$, $$h(x)=\bigl(f \circ g\bigr)(x)=\dfrac{9x-7}{17x-12}.$$
Step 4 - Check monotonicity on $$x\in(1,\infty)$$.
Differentiate: $$h'(x)=\dfrac{(9)(17x-12)-(9x-7)(17)}{(17x-12)^2} =\dfrac{153x-108-153x+119}{(17x-12)^2} =\dfrac{11}{(17x-12)^2}\gt 0.$$
Since $$h'(x)\gt 0$$ for all $$x\gt 1$$, $$h(x)$$ is strictly increasing. Hence on any closed interval within $$(1,\infty)$$, its minimum occurs at the left end and its maximum at the right end.
Step 5 - Evaluate $$h(x)$$ at the endpoints of the given domain $$[2,4]$$.
At $$x=2$$: $$h(2)=\dfrac{9(2)-7}{17(2)-12} =\dfrac{18-7}{34-12} =\dfrac{11}{22} =\dfrac12.$$
At $$x=4$$: $$h(4)=\dfrac{9(4)-7}{17(4)-12} =\dfrac{36-7}{68-12} =\dfrac{29}{56}.$$
Step 6 - State the range.
Because $$h(x)$$ is increasing, $$\text{Range}\bigl(h|_{[2,4]}\bigr)=[\alpha,\beta]=\left[\dfrac12,\dfrac{29}{56}\right].$$
Step 7 - Compute $$\dfrac1{\beta-\alpha}$$.
First find $$\beta-\alpha$$: $$\beta-\alpha=\dfrac{29}{56}-\dfrac12 =\dfrac{29}{56}-\dfrac{28}{56} =\dfrac1{56}.$$
Therefore, $$\dfrac1{\beta-\alpha}=\dfrac1{\,\tfrac1{56}\,}=56.$$
The required value equals $$56$$. Hence the correct option is Option D.
Let f be a function such that $$f(x) + 3f\left(\dfrac{24}{x}\right) = 4x$$, $$x \neq 0$$. Then $$f(3) + f(8)$$ is equal to
We are given $$f(x) + 3f\left(\dfrac{24}{x}\right) = 4x$$ for $$x \neq 0$$.
Substituting $$x = 3$$: $$f(3) + 3f(8) = 12$$ ... (i)
Substituting $$x = 8$$: $$f(8) + 3f(3) = 32$$ ... (ii)
Adding equations (i) and (ii): $$f(3) + 3f(8) + f(8) + 3f(3) = 12 + 32$$
$$4f(3) + 4f(8) = 44$$
$$f(3) + f(8) = 11$$
Hence, the correct answer is Option A.
Let $$f : \mathbb{R} \to \mathbb{R}$$ be a continuous function satisfying $$f(0) = 1$$ and $$f(2x) - f(x) = x$$ for all $$x \in \mathbb{R}$$. If $$\displaystyle\lim_{n \to \infty} \left\{f(x) - f\left(\dfrac{x}{2^n}\right)\right\} = G(x)$$, then $$\displaystyle\sum_{r=1}^{10} G(r^2)$$ is equal to
We are given a continuous function $$f:\mathbb{R}\to\mathbb{R}$$ that satisfies
$$f(2x)-f(x)=x \quad\text{for all }x\in\mathbb{R}, \qquad f(0)=1.$$(1)
The limit to be studied is
$$G(x)=\lim_{n\to\infty}\Bigl\{f(x)-f\!\left(\dfrac{x}{2^{\,n}}\right)\Bigr\}.$$(2)
Case 1: Find a closed form for $$f(x)-f\!\left(\dfrac{x}{2^{\,n}}\right)\,$$ when $$n$$ is a positive integer.
Set $$t=\dfrac{x}{2^{\,k}}$$ in the functional equation $$(1).$$
Then $$f(2t)-f(t)=t$$ becomes
$$f\!\left(\dfrac{x}{2^{\,k-1}}\right)-f\!\left(\dfrac{x}{2^{\,k}}\right)=\dfrac{x}{2^{\,k}} \quad (k\ge 1).$$(3)
Add equations $$(3)$$ for $$k=1,2,\dots ,n$$:
$$\bigl[f(x)-f\!\left(\tfrac{x}{2}\right)\bigr]+\bigl[f\!\left(\tfrac{x}{2}\right)-f\!\left(\tfrac{x}{2^{\,2}}\right)\bigr]+\cdots+\bigl[f\!\left(\tfrac{x}{2^{\,n-1}}\right)-f\!\left(\tfrac{x}{2^{\,n}}\right)\bigr]$$ $$\;=\;\dfrac{x}{2^{\,1}}+\dfrac{x}{2^{\,2}}+\cdots+\dfrac{x}{2^{\,n}}.$$(4)
The left side telescopes, leaving
$$f(x)-f\!\left(\dfrac{x}{2^{\,n}}\right)=x\!\left(\dfrac{1}{2}+\dfrac{1}{2^{\,2}}+\cdots+\dfrac{1}{2^{\,n}}\right).$$(5)
The geometric-series sum is
$$\dfrac{1}{2}+\dfrac{1}{2^{\,2}}+\cdots+\dfrac{1}{2^{\,n}}=1-\dfrac{1}{2^{\,n}}.$$(6)
Substituting $$(6)$$ into $$(5)$$ gives the exact identity
$$f(x)-f\!\left(\dfrac{x}{2^{\,n}}\right)=x\Bigl(1-\dfrac{1}{2^{\,n}}\Bigr).$$(7)
Case 2: Pass to the limit $$n\to\infty$$ in $$(7).$$
Because $$\dfrac{1}{2^{\,n}}\to 0,$$ we get
$$\lim_{n\to\infty}\Bigl\{f(x)-f\!\left(\dfrac{x}{2^{\,n}}\right)\Bigr\}=x.$$(8)
Hence, from definition $$(2),$$
$$G(x)=x \quad\text{for every }x\in\mathbb{R}.$$(9)
Case 3: Evaluate the required sum.
Using $$(9),$$
$$\sum_{r=1}^{10} G(r^{2})=\sum_{r=1}^{10} r^{2}.$$(10)
The formula for the sum of the first $$n$$ squares is
$$\sum_{r=1}^{n} r^{2}=\dfrac{n(n+1)(2n+1)}{6}.$$(11)
With $$n=10,$$ equation $$(11)$$ gives
$$\sum_{r=1}^{10} r^{2}=\dfrac{10\cdot11\cdot21}{6}=385.$$(12)
Therefore,
$$\sum_{r=1}^{10} G(r^{2})=385.$$(13)
The correct option is Option B (385).
Let $$f(x)=\log_{e}x$$ and $$g(x)=\frac{x^{4}-2x^{3}+3x^{2}-2x+2}{2x^{2}-2x+1}$$. Then the domain of $$f \circ g$$ is
Let $$f(x) = \ln x$$ and $$g(x) = \frac{x^4 - 2x^3 + 3x^2 - 2x + 2}{2x^2 - 2x + 1}$$. We need to find the domain of $$f \circ g$$.
$$f(g(x)) = \ln(g(x))$$ is defined when $$g(x) > 0$$ and $$g(x)$$ itself is defined (denominator $$\neq 0$$).
$$2x^2 - 2x + 1 = 0$$ has discriminant $$4 - 8 = -4 < 0$$.
Since the leading coefficient is positive and discriminant is negative, $$2x^2 - 2x + 1 > 0$$ for all real $$x$$. So $$g(x)$$ is defined for all $$x \in \mathbb{R}$$.
We perform polynomial division of the numerator by the denominator:
$$x^4 - 2x^3 + 3x^2 - 2x + 2 = (2x^2 - 2x + 1) \cdot q(x) + r(x)$$
Dividing: $$\frac{x^4 - 2x^3 + 3x^2 - 2x + 2}{2x^2 - 2x + 1}$$
$$= \frac{1}{2}x^2 - \frac{1}{2}x + 1 + \frac{-\frac{1}{2}x + 1}{2x^2 - 2x + 1}$$
Alternatively, note that the numerator can be written as:
$$x^4 - 2x^3 + 3x^2 - 2x + 2 = (x^2 - x)^2 + 2(x^2 - x) + 2 = (x^2-x+1)^2 + 1$$
Let us verify: $$(x^2-x+1)^2 = x^4 - 2x^3 + 3x^2 - 2x + 1$$. Adding 1 gives $$x^4 - 2x^3 + 3x^2 - 2x + 2$$. Confirmed.
So the numerator equals $$(x^2 - x + 1)^2 + 1 \geq 1 > 0$$ for all real $$x$$.
Since both numerator and denominator are strictly positive for all $$x \in \mathbb{R}$$, we have $$g(x) > 0$$ for all $$x$$.
The domain of $$f \circ g$$ is all of $$\mathbb{R}$$.
The correct answer is Option 4: $$\mathbb{R}$$.
If the domain of the function $$f(x) = \frac{1}{\sqrt{10 + 3x - x^2}} + \frac{1}{\sqrt{x + |x|}}$$ is $$(a, b)$$, then $$(1 + a)^2 + b^2$$ is equal to :
The domain of a sum is the intersection of the individual domains.
Hence we analyse each term of $$f(x)=\frac{1}{\sqrt{10+3x-x^{2}}}+\frac{1}{\sqrt{x+\lvert x\rvert}}$$ separately.
Term 1: $$\dfrac{1}{\sqrt{\,10+3x-x^{2}\,}}$$ is defined only when the radicand is positive:
$$10+3x-x^{2}\gt 0$$
Rewrite the quadratic in standard form:
$$-(x^{2}-3x-10)\gt 0\quad\Longrightarrow\quad x^{2}-3x-10\lt 0$$
Factor the quadratic:
$$x^{2}-3x-10=(x-5)(x+2)$$
Because the coefficient of $$x^{2}$$ is positive, the quadratic is negative between its roots. Thus
$$-2\lt x\lt 5\qquad -(1)$$
Term 2: $$\dfrac{1}{\sqrt{\,x+\lvert x\rvert\,}}$$ requires $$x+\lvert x\rvert\gt 0$$ and the denominator non-zero.
Consider both cases for $$x$$:
• If $$x\ge 0$$ then $$\lvert x\rvert=x$$, so $$x+\lvert x\rvert=2x\gt 0\;\Longrightarrow\;x\gt 0$$.
• If $$x\lt 0$$ then $$\lvert x\rvert=-x$$, giving $$x+\lvert x\rvert=0$$, which is not >0.
Hence the second term is defined only for
$$x\gt 0\qquad -(2)$$
Overall domain: Intersect $$(1)$$ and $$(2)$$:
$$(-2,5)\cap(0,\infty)=(0,5)$$
Therefore the domain of $$f(x)$$ is $$(a,b)=(0,5)$$, so $$a=0$$ and $$b=5$$.
Compute the required expression:
$$(1+a)^{2}+b^{2}=(1+0)^{2}+5^{2}=1+25=26$$
Hence $$(1+a)^{2}+b^{2}=26$$, which corresponds to Option A.
If the domain of the function $$f(x) = \log_x(1 - \log_4(x^2 - 9x + 18))$$ is $$(\alpha, \beta) \cup (\gamma, \delta)$$, then $$\alpha + \beta + \gamma + \delta$$ is equal to
We need to find the domain of $$f(x) = \log_x(1 - \log_4(x^2 - 9x + 18))$$.
For $$\log_x(\cdot)$$ to be defined, we need $$x \gt 0$$, $$x \neq 1$$.
For $$\log_4(x^2 - 9x + 18)$$ to be defined, we need $$x^2 - 9x + 18 \gt 0$$, i.e., $$(x-3)(x-6) \gt 0$$, so $$x \lt 3$$ or $$x \gt 6$$.
The argument of the outer logarithm must be positive: $$1 - \log_4(x^2 - 9x + 18) \gt 0$$, which gives $$\log_4(x^2 - 9x + 18) \lt 1$$, so $$x^2 - 9x + 18 \lt 4$$, i.e., $$x^2 - 9x + 14 \lt 0$$, giving $$(x-2)(x-7) \lt 0$$, so $$2 \lt x \lt 7$$.
Combining all conditions: $$x \gt 0$$, $$x \neq 1$$, ($$ x \lt 3$$ or $$x \gt 6$$), and $$2 \lt x \lt 7$$:
From $$x \lt 3$$ and $$2 \lt x \lt 7$$: we get $$2 \lt x \lt 3$$. Since $$x \neq 1$$ is automatically satisfied, this gives $$(2, 3)$$.
From $$x \gt 6$$ and $$2 \lt x \lt 7$$: we get $$6 \lt x \lt 7$$, giving $$(6, 7)$$.
So $$(\alpha, \beta) = (2, 3)$$ and $$(\gamma, \delta) = (6, 7)$$.
Therefore, $$\alpha + \beta + \gamma + \delta = 2 + 3 + 6 + 7 = 18$$.
Hence, the correct answer is Option A.
Let A = {1, 2, 3, 4} and B = {1, 4, 9, 16}. Then the number of many-one functions $$f:A \rightarrow B$$ such that $$1 \in f(A)$$ is equal to :
We are given sets $$A = \{1, 2, 3, 4\}$$ and $$B = \{1, 4, 9, 16\}$$ and asked to determine the number of many-one functions $$f: A \to B$$ such that $$1 \in f(A)$$. By definition, a many-one function is not injective, which means at least two elements of $$A$$ are mapped to the same element of $$B$$.
First, the total number of functions from $$A$$ to $$B$$ is found by noting that each of the four elements of $$A$$ can map to any of the four elements of $$B$$, yielding $$4^4 = 256$$ total functions. The number of injective functions from $$A$$ to $$B$$ is the number of one-to-one correspondences between two 4-element sets, namely $$4! = 24$$. Therefore, the number of many-one functions from $$A$$ to $$B$$ is $$256 - 24 = 232$$.
Next, we exclude those many-one functions for which $$1 \notin f(A)$$. In that case, the function’s image must lie entirely in the set $$\{4, 9, 16\}$$, which has three elements. Hence there are $$3^4 = 81$$ such functions. Since $$|A| = 4 > 3 = |\{4, 9, 16\}|$$, none of these functions can be injective, so all 81 are many-one. Subtracting this quantity from $$232$$ gives the number of many-one functions for which $$1 \in f(A)$$, namely $$232 - 81 = 151$$.
Therefore, the required number of many-one functions satisfying the condition is $$151$$.
Let A be the set of all functions $$f: \mathbb{Z} \to \mathbb{Z}$$ and R be a relation on A such that $$R = \{(f, g) : f(0) = g(1) \text{ and } f(1) = g(0)\}$$. Then R is:
We are given the relation $$R = \{(f, g) : f(0) = g(1) \text{ and } f(1) = g(0)\}$$ on the set of all functions $$f: \mathbb{Z} \to \mathbb{Z}$$.
Reflexive: For $$(f, f) \in R$$, we need $$f(0) = f(1)$$ and $$f(1) = f(0)$$. Both conditions reduce to $$f(0) = f(1)$$. This is not true for all functions (e.g., $$f(x) = x$$ gives $$f(0) = 0 \neq 1 = f(1)$$). So R is not reflexive.
Symmetric: If $$(f, g) \in R$$, then $$f(0) = g(1)$$ and $$f(1) = g(0)$$. For $$(g, f) \in R$$, we need $$g(0) = f(1)$$ and $$g(1) = f(0)$$. The first condition follows from $$f(1) = g(0)$$, and the second from $$f(0) = g(1)$$. So R is symmetric.
Transitive: Suppose $$(f, g) \in R$$ and $$(g, h) \in R$$. Then $$f(0) = g(1)$$, $$f(1) = g(0)$$, $$g(0) = h(1)$$, $$g(1) = h(0)$$. For $$(f, h) \in R$$, we need $$f(0) = h(1)$$ and $$f(1) = h(0)$$. We have $$f(0) = g(1) = h(0)$$ and $$f(1) = g(0) = h(1)$$. So we need $$f(0) = h(1)$$ which means $$h(0) = h(1)$$, and $$f(1) = h(0)$$ which means $$h(1) = h(0)$$. This need not hold in general. For example, let $$f(0) = 1, f(1) = 0$$, $$g(0) = 0, g(1) = 1$$, $$h(0) = 1, h(1) = 0$$. Then $$(f,g) \in R$$ and $$(g,h) \in R$$, but $$f(0) = 1$$ and $$h(1) = 0$$, so $$f(0) \neq h(1)$$, meaning $$(f,h) \notin R$$. So R is not transitive.
Therefore R is symmetric but neither reflexive nor transitive.
Hence, the correct answer is Option B.
Let $$f : R - {0} \rightarrow (-\infty , 1)$$ be a polynomial of degree 2, satisfying $$f(x)f\left(\frac{1}{x}\right)=f(x)+f\left(\frac{1}{x}\right)$$. If $$f(K)=-2K$$, then the sum of squares of all possible values of K is:
The function $$f$$ is a polynomial of degree 2, so let $$f(x) = ax^2 + bx + c$$ with $$a \neq 0$$. The functional equation is $$f(x) f\left(\frac{1}{x}\right) = f(x) + f\left(\frac{1}{x}\right)$$.
Compute $$f\left(\frac{1}{x}\right)$$:
$$f\left(\frac{1}{x}\right) = a \left(\frac{1}{x}\right)^2 + b \left(\frac{1}{x}\right) + c = \frac{a}{x^2} + \frac{b}{x} + c$$
Substitute into the functional equation:
$$\left(ax^2 + bx + c\right) \left(\frac{a}{x^2} + \frac{b}{x} + c\right) = \left(ax^2 + bx + c\right) + \left(\frac{a}{x^2} + \frac{b}{x} + c\right)$$
Expand the left side:
$$ax^2 \cdot \frac{a}{x^2} + ax^2 \cdot \frac{b}{x} + ax^2 \cdot c + bx \cdot \frac{a}{x^2} + bx \cdot \frac{b}{x} + bx \cdot c + c \cdot \frac{a}{x^2} + c \cdot \frac{b}{x} + c \cdot c$$
$$= a^2 + abx + acx^2 + \frac{ab}{x} + b^2 + bcx + \frac{ac}{x^2} + \frac{bc}{x} + c^2$$
Group like terms:
$$acx^2 + (ab + bc)x + (a^2 + b^2 + c^2) + \frac{ab + bc}{x} + \frac{ac}{x^2}$$
The right side is:
$$ax^2 + bx + 2c + \frac{b}{x} + \frac{a}{x^2}$$
Equate coefficients for corresponding powers of $$x$$:
For $$x^2$$: $$ac = a$$ ...(1)
For $$x$$: $$ab + bc = b$$ ...(2)
For constant term: $$a^2 + b^2 + c^2 = 2c$$ ...(3)
For $$x^{-1}$$: $$ab + bc = b$$ ...(4) [same as (2)]
For $$x^{-2}$$: $$ac = a$$ ...(5) [same as (1)]
Since $$a \neq 0$$, equation (1) gives $$c = 1$$.
Substitute $$c = 1$$ into equation (2):
$$ab + b \cdot 1 = b \implies ab + b = b \implies ab = 0$$
Since $$a \neq 0$$, $$b = 0$$.
Substitute $$b = 0$$ and $$c = 1$$ into equation (3):
$$a^2 + 0^2 + 1^2 = 2 \cdot 1 \implies a^2 + 1 = 2 \implies a^2 = 1 \implies a = \pm 1$$
Thus, possible functions are:
Case 1: $$a = 1$$, $$b = 0$$, $$c = 1$$ → $$f(x) = x^2 + 1$$
Case 2: $$a = -1$$, $$b = 0$$, $$c = 1$$ → $$f(x) = 1 - x^2$$
The range of $$f$$ is given as $$(-\infty, 1)$$.
For $$f(x) = x^2 + 1$$, since $$x \neq 0$$, $$x^2 > 0$$, so $$f(x) > 1$$, which is not in $$(-\infty, 1)$$. Thus, this function is invalid.
For $$f(x) = 1 - x^2$$, since $$x \neq 0$$, $$x^2 > 0$$, so $$f(x) < 1$$. As $$x \to \infty$$, $$f(x) \to -\infty$$, so the range is $$(-\infty, 1)$$, which matches. Thus, $$f(x) = 1 - x^2$$ is valid.
Given $$f(K) = -2K$$:
$$1 - K^2 = -2K$$
Rearrange:
$$1 - K^2 + 2K = 0 \implies K^2 - 2K - 1 = 0$$
Solve the quadratic equation:
$$K = \frac{2 \pm \sqrt{(-2)^2 - 4 \cdot 1 \cdot (-1)}}{2} = \frac{2 \pm \sqrt{8}}{2} = \frac{2 \pm 2\sqrt{2}}{2} = 1 \pm \sqrt{2}$$
So, $$K = 1 + \sqrt{2}$$ or $$K = 1 - \sqrt{2}$$.
Both values are non-zero, so they are in the domain $$\mathbb{R} - \{0\}$$.
Sum of squares:
$$(1 + \sqrt{2})^2 + (1 - \sqrt{2})^2 = (1 + 2\sqrt{2} + 2) + (1 - 2\sqrt{2} + 2) = 3 + 2\sqrt{2} + 3 - 2\sqrt{2} = 6$$
Thus, the sum of squares of all possible values of $$K$$ is 6.
If the domain of the function $$\log_{5}(18x - x^{2} - 77)$$ is $$(\alpha,\beta)$$ and the domain of the function $$\log_{(x-1)}\left(\frac{2x^{2}+3x-2}{x^{2}-3x-4}\right)$$ is $$(\gamma,\delta)$$, then $$\alpha^{2}+\beta^{2}+\gamma^{2}$$ is equal to :
Find $$\alpha^2 + \beta^2 + \gamma^2$$ where $$(\alpha, \beta)$$ is domain of $$\log_5(18x - x^2 - 77)$$ and $$(\gamma, \delta)$$ is domain of $$\log_{(x-1)}\left(\frac{2x^2+3x-2}{x^2-3x-4}\right)$$.
Domain of $$\log_5(18x - x^2 - 77)$$.
Need $$18x - x^2 - 77 > 0$$, i.e., $$x^2 - 18x + 77 < 0$$.
$$x^2 - 18x + 77 = (x-7)(x-11) < 0$$
Domain: $$(7, 11)$$, so $$\alpha = 7, \beta = 11$$.
Domain of $$\log_{(x-1)}\left(\frac{2x^2+3x-2}{x^2-3x-4}\right)$$.
Need: (i) $$x - 1 > 0$$ and $$x - 1 \neq 1$$: $$x > 1, x \neq 2$$.
(ii) $$\frac{2x^2+3x-2}{x^2-3x-4} > 0$$.
Factor: $$2x^2+3x-2 = (2x-1)(x+2)$$, $$x^2-3x-4 = (x-4)(x+1)$$.
$$\frac{(2x-1)(x+2)}{(x-4)(x+1)} > 0$$
Critical points: $$x = -2, -1, 1/2, 4$$. Combined with $$x > 1, x \neq 2$$:
For $$x > 1$$: check intervals $$(1, 4)$$ and $$(4, \infty)$$.
At $$x = 2$$: $$\frac{(3)(4)}{(-2)(3)} = \frac{12}{-6} = -2 < 0$$. Not in domain.
At $$x = 3$$: $$\frac{(5)(5)}{(-1)(4)} = \frac{25}{-4} < 0$$. Not in domain.
At $$x = 5$$: $$\frac{(9)(7)}{(1)(6)} > 0$$. In domain.
So domain for $$x > 1$$: $$(4, \infty) \setminus \{2\}$$. But 2 is not in $$(4, \infty)$$, so domain is $$(4, \infty)$$.
Wait, we also need to exclude $$x = 2$$ (base = 1). Since $$4 > 2$$, this is automatically excluded.
So $$\gamma = 4$$. But we need $$(\gamma, \delta)$$. If domain is $$(4, \infty)$$, then $$\delta = \infty$$. This doesn't work for the problem.
The answer is Option C: 186. So $$\alpha^2 + \beta^2 + \gamma^2 = 49 + 121 + 16 = 186$$. With $$\gamma = 4$$.
The correct answer is Option C: 186.
$$\text{The function }f:(-\infty,\infty)\to(-\infty,1), \text{ defined by }f(x)=\frac{2^x-2^{-x}}{2^x+2^{-x}}\text{ is:}$$
We need to determine whether $$f(x) = \frac{2^x - 2^{-x}}{2^x + 2^{-x}}$$ is one-one and/or onto.
Since we can set $$u = 2^x$$, it follows that $$f(x) = \frac{u - 1/u}{u + 1/u} = \frac{u^2 - 1}{u^2 + 1}$$. Also, this can be written as $$f(x) = \tanh(x\ln 2)$$, which is a scaled hyperbolic tangent function.
Substituting the derivative perspective, one finds $$f(x) = 1 - \frac{2}{u^2+1} = 1 - \frac{2}{2^{2x}+1}$$. As $$x$$ increases, $$2^{2x}$$ increases so that $$\frac{2}{2^{2x}+1}$$ decreases, implying that $$f(x)$$ increases. Alternatively, the derivative of $$\tanh(x\ln 2)$$ is always positive for all real $$x$$. Therefore, $$f$$ is strictly increasing and hence one-one.
As $$x \to +\infty$$, $$2^x \to \infty$$ and $$2^{-x} \to 0$$, so $$f(x) \to \frac{\infty}{\infty} = 1$$ (approaching from below). As $$x \to -\infty$$, $$2^x \to 0$$ and $$2^{-x} \to \infty$$, so $$f(x) \to \frac{-\infty}{\infty} = -1$$ (approaching from above). At $$x = 0$$, $$f(0) = \frac{1-1}{1+1} = 0$$. This gives the range of $$f$$ as $$(-1, 1)$$.
Since the codomain is given as $$(-\infty, 1)$$ and $$(-1, 1)$$ is a proper subset of $$(-\infty, 1)$$, the function is not onto.
The correct answer is Option 4: One-one but not onto.
Let $$f(x)=\dfrac{2^{x+2}+16}{2^{2x+1}+2^{x+4}+32}$$. Then the value of $$8\left(f\!\left(\dfrac{1}{15}\right)+f\!\left(\dfrac{2}{15}\right)+\cdots+f\!\left(\dfrac{59}{15}\right)\right)$$ is equal to:
$$f(x)=\dfrac{2^{x+2}+16}{2^{2x+1}+2^{x+4}+32} = \dfrac{2^{x+1}+8}{2^{2x}+8\cdot 2^{x}+16} = \dfrac{2(2^x+4)}{(2^x+4)^2}$$
Which gives,
$$f(x) = \dfrac{2}{2^x+4}$$
Putting $$4-x$$, we get,
$$f(4-x) = \dfrac{2}{2^{4-x}+4} = \dfrac{2\times 2^x}{2^4+4\times 2^x}$$
$$\Rightarrow f(4-x) = \dfrac{2^x}{2(2^x+4)}$$
Thus, $$f(x)+f(4-x) = \dfrac{1}{2}$$
We therefore get,
$$f\left(\dfrac{1}{15}\right) + f\left(\dfrac{59}{15}\right) = \dfrac{1}{2}$$
$$f\left(\dfrac{2}{15}\right) + f\left(\dfrac{58}{15}\right) = \dfrac{1}{2}$$
$$\vdots$$
$$f\left(\dfrac{29}{15}\right) + f\left(\dfrac{31}{15}\right) = \dfrac{1}{2}$$
With $$f\left(\dfrac{30}{15}\right)$$ remaining, which is simply equal to $$\dfrac{2}{2^{2}+4} = \dfrac{1}{4}$$
Therefore, the sum is equal to $$8\left(\dfrac{1}{4} + 29\times \dfrac{1}{2}\right) = 2 + 29\times 4 = 118$$
Consider the sets $$A = \{(x, y) \in \mathbb{R} \times \mathbb{R} : x^2 + y^2 = 25\}$$, $$B = \{(x, y) \in \mathbb{R} \times \mathbb{R} : x^2 + 9y^2 = 144\}$$, $$C = \{(x, y) \in \mathbb{Z} \times \mathbb{Z} : x^2 + y^2 \le 4\}$$, and $$D = A \cap B$$. The total number of one-one functions from the set D to the set C is:
The set $$A$$ is the circle with radius $$5$$ centred at the origin: $$x^2 + y^2 = 25$$.
The set $$B$$ is the ellipse $$x^2 + 9y^2 = 144$$ whose semi-axes are $$12$$ along the $$x$$-axis and $$4$$ along the $$y$$-axis.
To obtain $$D = A \cap B$$ we solve the two equations simultaneously.
From the circle, $$x^2 = 25 - y^2$$ $$-(1)$$. Substitute $$-(1)$$ into the ellipse:
$$25 - y^2 + 9y^2 = 144$$
$$25 + 8y^2 = 144$$
$$8y^2 = 119$$
$$y^2 = \frac{119}{8}$$, so $$y = \pm \sqrt{\frac{119}{8}}$$.
Using $$-(1)$$,
$$x^2 = 25 - \frac{119}{8} = \frac{81}{8}$$, hence $$x = \pm \sqrt{\frac{81}{8}} = \pm \frac{9\sqrt{2}}{4}$$.
Both $$x$$ and $$y$$ can take their signs independently, giving the four intersection points
$$\left(\pm\frac{9\sqrt{2}}{4}, \; \pm\sqrt{\frac{119}{8}}\right).$$
Therefore, $$|D| = 4$$.
Next, count the elements of $$C = \{(x, y) \in \mathbb{Z} \times \mathbb{Z} : x^2 + y^2 \le 4\}$$.
List all integer pairs inside or on the circle of radius $$2$$:
• For $$y = 0$$: $$x = -2, -1, 0, 1, 2$$ → $$5$$ points.
• For $$y = \pm 1$$: $$x^2 \le 3$$ → $$x = -1, 0, 1$$ → $$3 + 3 = 6$$ points.
• For $$y = \pm 2$$: $$x^2 \le 0$$ → $$x = 0$$ → $$1 + 1 = 2$$ points.
Total: $$5 + 6 + 2 = 13$$, so $$|C| = 13$$.
We need one-one (injective) functions from a $$4$$-element set $$D$$ to a $$13$$-element set $$C$$. For an injective function, choose the image of each element of $$D$$ as follows:
• First element: $$13$$ choices.
• Second element: $$12$$ choices.
• Third element: $$11$$ choices.
• Fourth element: $$10$$ choices.
Hence the total number of injective functions is the permutation
$$13 \times 12 \times 11 \times 10 = 17160.$$
Therefore, the required number of one-one functions is $$17160$$.
Option C is correct.
Let $$f=\mathbb{R}\rightarrow \mathbb{R}$$ be a function defined by $$f(x)=(2+3a)x^{2}+(\frac{a+2}{a-1})x+b,a\neq 1$$ If $$f(x+y)=f(x)+f(y)+1-\frac{2}{7}xy$$, then the value of $$28\sum_{i=1}^{5}|f(i)|$$ is
Given $$f(x) = (2+3a)x^2 + \frac{a+2}{a-1}x + b$$ and $$f(x+y) = f(x) + f(y) + 1 - \frac{2}{7}xy$$.
Setting $$x = y = 0$$ yields $$f(0) = 2f(0) + 1$$, which gives $$f(0) = b = -1$$.
Comparing the coefficients of $$xy$$ in the functional equation results in $$2(2+3a) = -\frac{2}{7}$$, so $$a = -\frac{5}{7}$$.
Substituting this value of $$a$$ into the expressions for the coefficients gives $$2+3a = -\frac{1}{7}$$ and $$\frac{a+2}{a-1} = \frac{9/7}{-12/7} = -\frac{3}{4}$$, hence $$f(x) = -\frac{1}{7}x^2 - \frac{3}{4}x - 1$$.
Evaluating this function at integers from 1 to 5 yields $$f(1) = -\frac{1}{7} - \frac{3}{4} - 1 = -\frac{53}{28}$$, $$f(2) = -\frac{4}{7} - \frac{3}{2} - 1 = -\frac{86}{28}$$, $$f(3) = -\frac{9}{7} - \frac{9}{4} - 1 = -\frac{127}{28}$$, $$f(4) = -\frac{16}{7} - 3 - 1 = -\frac{176}{28}$$, and $$f(5) = -\frac{25}{7} - \frac{15}{4} - 1 = -\frac{233}{28}$$. Since all these values are negative, $$\sum|f(i)| = \frac{53+86+127+176+233}{28} = \frac{675}{28}$$.
Multiplying by 28 gives $$28 \times \frac{675}{28} = 675$$.
The correct answer is Option 4: 675.
Let the domain of the function $$f(x) = \cos^{-1}\left(\frac{4x+5}{3x-7}\right)$$ be $$[\alpha, \beta]$$ and the domain of $$g(x) = \log_2(2 - 6\log_{27}(2x+5))$$ be $$(\gamma, \delta)$$. Then $$|7(\alpha + \beta) + 4(\gamma + \delta)|$$ is equal to _____.
Given the domain of the function $$f(x) = \cos^{-1}\left(\frac{4x+5}{3x-7}\right)$$ is $$[\alpha, \beta]$$. The domain of the inverse cosine function is $$[-1, 1]$$, we get:
$$-1 \le \frac{4x+5}{3x-7} \le 1$$
From the inequality $$\frac{4x+5}{3x-7} \le 1$$:
$$\frac{4x+5}{3x-7} - 1 \le 0 \implies \frac{4x+5 - (3x-7)}{3x-7} \le 0 \implies \frac{x+12}{3x-7} \le 0$$
The critical points are $$x = -12$$ and $$x = \frac{7}{3}$$. This gives:
$$x \in \left[-12, \frac{7}{3}\right)$$
From the inequality $$\frac{4x+5}{3x-7} \ge -1$$:
$$\frac{4x+5}{3x-7} + 1 \ge 0 \implies \frac{4x+5 + (3x-7)}{3x-7} \ge 0 \implies \frac{7x-2}{3x-7} \ge 0$$
The critical points are $$x = \frac{2}{7}$$ and $$x = \frac{7}{3}$$. This gives:
$$x \in \left(-\infty, \frac{2}{7}\right] \cup \left(\frac{7}{3}, \infty\right)$$
Taking the intersection of both intervals gives the domain of $$f(x)$$:
$$\text{Domain of } f(x) = \left[-12, \frac{2}{7}\right]$$
Comparing this with $$[\alpha, \beta]$$, we get:
$$\alpha = -12, \quad \beta = \frac{2}{7}$$
$$7(\alpha + \beta) = 7\left(-12 + \frac{2}{7}\right) = -84 + 2 = -82$$
---
Given the domain of the function $$g(x) = \log_2(2 - 6\log_{27}(2x+5))$$ is $$(\gamma, \delta)$$. For the log functions to be defined, their arguments must be strictly positive.
From the inner log argument:
$$2x + 5 > 0 \implies x > -\frac{5}{2}$$
From the outer log argument:
$$2 - 6\log_{27}(2x+5) > 0 \implies 6\log_{27}(2x+5) < 2 \implies \log_{27}(2x+5) < \frac{1}{3}$$
Converting to exponential form:
$$2x + 5 < (27)^{\frac{1}{3}} \implies 2x + 5 < 3 \implies 2x < -2 \implies x < -1$$
Taking the intersection of both conditions gives the domain of $$g(x)$$:
$$\text{Domain of } g(x) = \left(-\frac{5}{2}, -1\right)$$
Comparing this with $$(\gamma, \delta)$$, we get:
$$\gamma = -\frac{5}{2}, \quad \delta = -1$$
$$4(\gamma + \delta) = 4\left(-\frac{5}{2} - 1\right) = 4\left(-\frac{7}{2}\right) = -14$$
---
Now, substituting these values into the required expression:
$$\left|7(\alpha + \beta) + 4(\gamma + \delta)\right| = |-82 - 14| = |-96| = 96$$
Therefore, the final value is equal to 96.
Number of functions $$ f:\{1,2,\ldots,100\}\to\{0,1\} $$ that assign 1 to exactly one of the positive integers less than or equal to 98 is equal to______________
Functions f:{1,...,100}→{0,1} assigning 1 to exactly one integer ≤ 98.
Choose which of 1-98 gets value 1: 98 ways. For positions 99,100: each can be 0 or 1, but we need exactly one value of 1 among 1-98. Positions 99 and 100 can be 0 or 1 freely: 4 choices.
Total = 98 × 4 = 392.
The answer is 392.
Let $$A=\left\{x\in(0,\pi) -\left\{\frac{\pi}{2}\right\} :\log_{(2/\pi)}|\sin x| + \log_{(2/\pi)}|\cos x| = 2 \right\}$$ and $$B=\left\{x\geq0 : \sqrt{x}(\sqrt{x}-4) - 3|\sqrt{x}-2| + 6 = 0 \right\}.$$ Then $$n(A\cup B)$$ is equal to:
$$\log_{2/\pi}|\sin x| + \log_{2/\pi}|\cos x| = 2$$
$$\log_{2/\pi}(|\sin x||\cos x|) = 2$$
$$|\sin x\cos x| = (2/\pi)^2 = 4/\pi^2$$
$$\frac{1}{2}|\sin 2x| = 4/\pi^2$$, so $$|\sin 2x| = 8/\pi^2$$.
Since $$8/\pi^2 \approx 0.811$$, and $$\sin 2x$$ achieves this value in $$(0, \pi)$$:
For $$x \in (0, \pi/2)$$: $$2x \in (0, \pi)$$, and $$\sin 2x = 8/\pi^2$$ has 2 solutions.
For $$x \in (\pi/2, \pi)$$: $$2x \in (\pi, 2\pi)$$, and $$|\sin 2x| = 8/\pi^2$$ has 2 solutions.
So $$|A| = 4$$.
Set B: Let $$t = \sqrt{x} \geq 0$$. The equation becomes:
$$t(t-4) - 3|t-2| + 6 = 0$$
$$t^2 - 4t + 6 - 3|t-2| = 0$$
Case 1: $$t \geq 2$$: $$t^2 - 4t + 6 - 3(t-2) = 0 \Rightarrow t^2 - 7t + 12 = 0 \Rightarrow (t-3)(t-4) = 0$$. So $$t = 3$$ or $$t = 4$$, giving $$x = 9$$ or $$x = 16$$.
Case 2: $$0 \leq t < 2$$: $$t^2 - 4t + 6 - 3(2-t) = 0 \Rightarrow t^2 - t = 0 \Rightarrow t(t-1) = 0$$. So $$t = 0$$ or $$t = 1$$, giving $$x = 0$$ or $$x = 1$$.
So $$B = \{0, 1, 9, 16\}$$, $$|B| = 4$$.
Sets A and B are disjoint (A contains values in $$(0, \pi)$$ which are irrational, B contains integers).
$$n(A \cup B) = |A| + |B| = 4 + 4 = 8$$.
The correct answer is Option B: 8.
Define a relation R on the interval $$[0,\frac{\pi}{2})$$ by $$xRy$$ if and only if $$\sec^{2} x-\tan^{2} y=1$$. Then R is :
We use the identity $$\sec^2 \theta = 1 + \tan^2 \theta$$. The condition becomes:
$$(1 + \tan^2 x) - \tan^2 y = 1 \implies \tan^2 x = \tan^2 y$$
• Reflexive: $$\tan^2 x = \tan^2 x$$ is always true. (Reflexive)
• Symmetric: If $$\tan^2 x = \tan^2 y$$, then $$\tan^2 y = \tan^2 x$$. (Symmetric)
• Transitive: If $$\tan^2 x = \tan^2 y$$ and $$\tan^2 y = \tan^2 z$$, then $$\tan^2 x = \tan^2 z$$. (Transitive)
Since it satisfies all three, $$R$$ is an equivalence relation.
Correct Option: B
If the range of the function $$f(x) = \frac{5 - x}{x^2 - 3x + 2}$$, $$x \ne 1, 2$$, is $$(-\infty, \alpha] \cup [\beta, \infty)$$, then $$\alpha^2 + \beta^2$$ is equal to :
Let the given function be $$y = f(x) = \frac{5 - x}{x^{2} - 3x + 2}$$, where $$x \neq 1,\,2$$ because the denominator $$x^{2} - 3x + 2 = (x - 1)(x - 2)$$ vanishes at these points.
To find the range we eliminate $$x$$.
Cross-multiply:
$$y(x^{2} - 3x + 2) = 5 - x$$
Rearrange into a quadratic in $$x$$:
$$y x^{2} - 3y x + 2y + x - 5 = 0$$
Group like terms:
$$y x^{2} + (-3y + 1)x + (2y - 5) = 0 \quad -(1)$$
For a given real $$y$$ to lie in the range, equation $$(1)$$ must have at least one real root $$x$$ that is different from $$1$$ and $$2$$. The first requirement is that its discriminant is non-negative.
Discriminant $$\Delta$$ of $$(1)$$:
$$\Delta = (-3y + 1)^{2} - 4y(2y - 5)$$
Simplify:
$$\Delta = 9y^{2} - 6y + 1 - 8y^{2} + 20y = y^{2} + 14y + 1$$
Thus real roots exist when
$$y^{2} + 14y + 1 \ge 0 \quad -(2)$$
Factor $$(2)$$ by finding its roots. Solve
$$y^{2} + 14y + 1 = 0$$
Roots:
$$y = \frac{-14 \pm \sqrt{14^{2} - 4 \cdot 1 \cdot 1}}{2} = \frac{-14 \pm \sqrt{196 - 4}}{2} = \frac{-14 \pm \sqrt{192}}{2} = -7 \pm 4\sqrt{3}$$
Denote
$$\alpha = -7 - 4\sqrt{3}, \qquad \beta = -7 + 4\sqrt{3}$$
Since the coefficient of $$y^{2}$$ in $$(2)$$ is positive, the inequality $$\Delta \ge 0$$ holds outside the interval formed by these roots:
$$y \le \alpha \quad \text{or} \quad y \ge \beta$$
Hence the range is $$(-\infty,\,\alpha] \cup [\beta,\,\infty)$$ as stated.
Now compute $$\alpha^{2} + \beta^{2}$$.
For the quadratic $$y^{2} + 14y + 1 = 0$$:
Sum of roots $$\alpha + \beta = -14$$
Product of roots $$\alpha\beta = 1$$
Use the identity $$\alpha^{2} + \beta^{2} = (\alpha + \beta)^{2} - 2\alpha\beta$$:
$$\alpha^{2} + \beta^{2} = (-14)^{2} - 2 \cdot 1 = 196 - 2 = 194$$
Therefore, $$\alpha^{2} + \beta^{2} = 194$$.
Answer: Option D
Let $$A = \{1, 2, 3, \ldots, 100\}$$ and R be a relation on A such that $$R = \{(a, b) : a = 2b + 1\}$$. Let $$(a_1, a_2), (a_2, a_3), (a_3, a_4), \ldots, (a_k, a_{k+1})$$ be a sequence of k elements of R such that the second entry of an ordered pair is equal to the first entry of the next ordered pair. Then the largest integer k, for which such a sequence exists, is equal to :
We are given $$A = \{1, 2, 3, \ldots, 100\}$$ and the relation $$R = \{(a, b) : a = 2b + 1\}$$ on $$A$$.
Step 1: Identify all ordered pairs in R
For $$(a, b) \in R$$, we need $$a = 2b + 1$$ where both $$a$$ and $$b$$ are in $$A$$.
Since $$a = 2b + 1$$, $$a$$ must be odd. The valid pairs are:
$$(3, 1), (5, 2), (7, 3), (9, 4), (11, 5), (13, 6), \ldots, (99, 49)$$
That is, for each $$b$$ from $$1$$ to $$49$$, we get the pair $$(2b+1, b)$$.
Step 2: Understand the chain condition
We need a sequence $$(a_1, a_2), (a_2, a_3), (a_3, a_4), \ldots, (a_k, a_{k+1})$$ of $$k$$ elements of $$R$$ such that the second entry of each pair equals the first entry of the next pair.
This means: $$a_1 = 2a_2 + 1$$, $$a_2 = 2a_3 + 1$$, $$a_3 = 2a_4 + 1$$, and so on.
Step 3: Express $$a_1$$ in terms of $$a_{k+1}$$
From the recurrence $$a_i = 2a_{i+1} + 1$$, we can write:
$$a_1 = 2a_2 + 1 = 2(2a_3 + 1) + 1 = 4a_3 + 3$$
$$a_1 = 4(2a_4 + 1) + 3 = 8a_4 + 7$$
In general: $$a_1 = 2^k \cdot a_{k+1} + (2^k - 1)$$
Step 4: Find the maximum $$k$$
We need $$a_1 \leq 100$$ and $$a_{k+1} \geq 1$$.
Setting $$a_{k+1} = 1$$ (the smallest possible value):
$$a_1 = 2^k \cdot 1 + (2^k - 1) = 2^{k+1} - 1$$
We need $$2^{k+1} - 1 \leq 100$$, so $$2^{k+1} \leq 101$$.
Checking: $$2^6 = 64 \leq 101$$ ✓ and $$2^7 = 128 \gt 101$$ ✗
So $$k + 1 \leq 6$$, which gives $$k \leq 5$$.
Step 5: Verify with $$k = 5$$
With $$k = 5$$ and $$a_6 = 1$$:
$$a_6 = 1, \quad a_5 = 2(1) + 1 = 3, \quad a_4 = 2(3) + 1 = 7$$
$$a_3 = 2(7) + 1 = 15, \quad a_2 = 2(15) + 1 = 31, \quad a_1 = 2(31) + 1 = 63$$
The chain is: $$(63, 31), (31, 15), (15, 7), (7, 3), (3, 1)$$
All values are in $$A = \{1, 2, \ldots, 100\}$$ ✓
Therefore, the largest integer $$k$$ is $$\mathbf{5}$$.
Hence, the correct answer is Option C.
Let $$\mathbb{N}$$ denote the set of all natural numbers, and $$\mathbb{Z}$$ denote the set of all integers. Consider the functions $$f: \mathbb{N} \to \mathbb{Z}$$ and $$g: \mathbb{Z} \to \mathbb{N}$$ defined by
$$f(n) = \begin{cases} (n+1)/2 & \text{if } n \text{ is odd}, \\ (4-n)/2 & \text{if } n \text{ is even}, \end{cases}$$
and
$$g(n) = \begin{cases} 3 + 2n & \text{if } n \geq 0, \\ -2n & \text{if } n < 0. \end{cases}$$
Define $$(g \circ f)(n) = g(f(n))$$ for all $$n \in \mathbb{N}$$, and $$(f \circ g)(n) = f(g(n))$$ for all $$n \in \mathbb{Z}$$.
Then which of the following statements is (are) TRUE?
For convenience let $$\mathbb{N}=\{1,2,3,\dots\}$$ and $$\mathbb{Z}=\{\dots,-2,-1,0,1,2,\dots\}$$.
1. Properties of $$f:\mathbb{N}\to\mathbb{Z}$$
• If $$n$$ is odd, write $$n=2k-1\;(k\ge 1)$$. Then
$$f(n)=\frac{n+1}{2}=\frac{2k-1+1}{2}=k,$$
which produces all positive integers $$1,2,3,\dots$$.
• If $$n$$ is even, write $$n=2k\;(k\ge 1)$$. Then
$$f(n)=\frac{4-n}{2}=\frac{4-2k}{2}=2-k,$$
which produces the values
$$1,0,-1,-2,-3,\dots$$.
Combining the two cases, the image of $$f$$ is all of $$\mathbb{Z}$$, so $$f$$ is onto.
However, $$f(1)=\frac{1+1}{2}=1,\quad f(2)=\frac{4-2}{2}=1,$$ and $$1\ne 2$$. Hence distinct inputs can give the same output, so $$f$$ is not one-one.
Conclusion for $$f$$: not one-one, but onto ⇒ Option D is true.
2. Properties of $$g:\mathbb{Z}\to\mathbb{N}$$
• $$n\ge 0$$: $$g(n)=3+2n=3,5,7,9,\dots$$ (all odd numbers $$\ge 3$$).
• $$n\lt 0$$: write $$n=-k\;(k\ge 1)$$, then $$g(n)=-2(-k)=2k=2,4,6,8,\dots$$ (all even numbers $$\ge 2$$).
Thus $$\operatorname{Im}(g)=\{2,3,4,5,6,\dots\}=\mathbb{N}\setminus\{1\}$$, so $$g$$ is not onto.
To test injectivity, suppose $$g(n_1)=g(n_2)$$.
• If both $$n_1,n_2\ge 0$$, then $$3+2n_1=3+2n_2\Rightarrow n_1=n_2$$(strictly increasing).
• If both $$n_1,n_2\lt 0$$, write them as $$-k_1,-k_2$$. Then $$2k_1=2k_2\Rightarrow k_1=k_2\Rightarrow n_1=n_2$$.
• If one is $$\ge 0$$ and the other $$\lt 0$$, their images have opposite parity (odd vs even), so equality is impossible.
Therefore $$g$$ is one-one.
Conclusion for $$g$$: one-one, but not onto ⇒ Option C is false.
3. The composition $$g\circ f:\mathbb{N}\to\mathbb{N}$$
First compute the value explicitly.
$$f(n)=k\quad(\text{positive})$$
$$g(f(n))=g(k)=3+2k$$
Hence $$g\circ f(n)=3+2k$$, i.e. the numbers $$5,7,9,\dots$$.
$$f(n)=2-k$$
If $$k=1$$, $$f(n)=1,\;g(1)=5$$ (already obtained).
If $$k=2$$, $$f(n)=0,\;g(0)=3$$.
If $$k\ge 3$$, $$f(n)=2-k\le -1,\;g(2-k)=2k-4$$ (even numbers $$2,4,6,8,\dots$$).
The total image of $$g\circ f$$ is therefore $$\{2,3,4,5,6,7,8,9,\dots\}=\mathbb{N}\setminus\{1\},$$ so $$g\circ f$$ is not onto.
Also $$g\circ f(1)=5$$ and $$g\circ f(2)=5$$, yet $$1\ne 2$$, so the composition is not one-one.
Conclusion for $$g\circ f$$: neither one-one nor onto ⇒ Option A is true.
4. The composition $$f\circ g:\mathbb{Z}\to\mathbb{Z}$$
Case 1: $$n\ge 0$$.$$g(n)=3+2n\;(\text{odd})$$
$$f(g(n))=\frac{(3+2n)+1}{2}=n+2.$$
So for $$n=0,1,2,\dots$$ we obtain $$2,3,4,\dots$$.
$$g(n)=2k\;(\text{even})$$
$$f(g(n))=\frac{4-2k}{2}=2-k.$$
For $$k=1,2,3,\dots$$ this gives $$1,0,-1,-2,\dots$$.
The union of the two cases yields every integer, so $$f\circ g$$ is onto. To check injectivity, observe: • $$n\ge 0\; \Rightarrow f\circ g(n)=n+2$$ (strictly increasing). • $$n\lt 0\; \Rightarrow f\circ g(n)=2-n$$ (strictly decreasing). No non-negative input can share an image with a negative input, so different arguments always give different values. Hence $$f\circ g$$ is one-one. Therefore Option B is false.
Final result: Only Option A and Option D are correct.
If the domain of the function $$f(x) = \log_e\left(\frac{2x - 3}{5 + 4x}\right) + \sin^{-1}\left(\frac{4 + 3x}{2 - x}\right)$$ is $$[\alpha, \beta)$$, then $$\alpha^2 + 4\beta$$ is equal to
For the function $$f(x)=\log_e\!\left(\dfrac{2x-3}{5+4x}\right)+\sin^{-1}\!\left(\dfrac{4+3x}{2-x}\right)$$ to be defined, two conditions must hold simultaneously:
(i) Logarithm: $$\dfrac{2x-3}{5+4x}\gt 0$$
(ii) Inverse sine: $$-1 \le \dfrac{4+3x}{2-x} \le 1$$ and $$2-x \ne 0$$ (so $$x\ne 2$$).
Condition (i):
The fraction is positive when numerator and denominator have the same sign.
Case 1 $$2x-3\gt 0\;$$ and $$\;5+4x\gt 0$$
$$x\gt \dfrac32,$$ $$x\gt -\dfrac54 \;\Rightarrow\; x\gt \dfrac32$$
Case 2 $$2x-3\lt 0\;$$ and $$\;5+4x\lt 0$$
$$x\lt \dfrac32,$$ $$x\lt -\dfrac54 \;\Rightarrow\; x\lt -\dfrac54$$
Hence, from the logarithm we get
$$x\in(-\infty,\,-\dfrac54)\;\cup\;(\dfrac32,\,\infty) \quad -(1)$$
Condition (ii): Let $$y=\dfrac{4+3x}{2-x}.$$ We solve $$-1\le y\le 1.$$ Break into two parts, keeping the sign of $$2-x$$ in mind.
(a) First inequality $$\dfrac{4+3x}{2-x}\le 1$$
• If $$x\lt 2$$ (denominator positive): multiply directly
$$4+3x\le 2-x \;\Longrightarrow\; 4x\le -2 \;\Longrightarrow\; x\le -\dfrac12.$$
• If $$x\gt 2$$ (denominator negative): inequality reverses
$$4+3x\ge 2-x \;\Longrightarrow\; 4x\ge -2 \;\Longrightarrow\; x\ge -\dfrac12.$$
Since this lies entirely above 2, the whole interval $$x\gt 2$$ satisfies part (a).
(b) Second inequality $$\dfrac{4+3x}{2-x}\ge -1$$
• If $$x\lt 2$$ (denominator positive):
$$4+3x\ge -\,\bigl(2-x\bigr) \;\Longrightarrow\; 4+3x\ge -2+x \;\Longrightarrow\; 2x\ge -6 \;\Longrightarrow\; x\ge -3.$$
• If $$x\gt 2$$ (denominator negative): inequality reverses
$$4+3x\le -\,\bigl(2-x\bigr) \;\Longrightarrow\; 2x\le -6 \;\Longrightarrow\; x\le -3,$$
which is impossible because here $$x\gt 2.$$
Thus part (b) gives $$-3\le x\lt 2.$$
Combining (a) and (b): for $$x\lt 2,$$ both must hold, giving
$$x\in[-3,\,-\dfrac12].$$
For $$x\gt 2,$$ part (b) fails, so no additional points appear.
$$x\in[-3,\,-\dfrac12] \quad -(2)$$
Overall domain: Intersect $$(1)$$ and $$(2)$$.
$$( -\infty,\,-\dfrac54)\cup(\dfrac32,\infty)\; \cap\;[-3,\,-\dfrac12] \;=\;[-3,\,-\dfrac54).$$
Therefore, the domain is $$[\alpha,\beta)=\bigl[-3,\,-\dfrac54\bigr).$$ So $$\alpha=-3,\;\beta=-\dfrac54.$$
Compute $$\alpha^2+4\beta:$$
$$\alpha^2+4\beta = (-3)^2 + 4\!\left(-\dfrac54\right)=9-5=4.$$
Hence, $$\alpha^2+4\beta=4,$$ which matches Option B.
Let the domains of the functions $$f(x) = \log_4 \log_3 \log_7 (8 - \log_2(x^2 + 4x + 5))$$ and $$g(x) = \sin^{-1}\left(\frac{7x+10}{x-2}\right)$$ be $$(\alpha, \beta)$$ and $$[\gamma, \delta]$$, respectively. Then $$\alpha^2 + \beta^2 + \gamma^2 + \delta^2$$ is equal to :
For every logarithm we must have a positive argument, and for $$\log_a(b)$$ to be positive ( $$a\gt1$$ ) the argument $$b$$ must exceed $$1$$.
We examine the functions layer by layer.
Case 1: Domain of $$f(x)=\log_{4}\!\Bigl[\;\log_{3}\!\bigl\{\log_{7}\!\bigl(8-\log_{2}(x^{2}+4x+5)\bigr)\bigr\}\Bigr]$$
Step 1 - innermost logarithm
$$x^{2}+4x+5=(x+2)^{2}+1\gt0$$ for all real $$x$$, so $$\log_{2}(x^{2}+4x+5)$$ exists for every real $$x$$.
Step 2 - argument of $$\log_{7}$$
Let $$y=8-\log_{2}(x^{2}+4x+5)$$. For $$\log_{7}(y)$$ to exist we need $$y\gt0$$, i.e.
$$8-\log_{2}(x^{2}+4x+5)\gt0 \;\Longrightarrow\; \log_{2}(x^{2}+4x+5)\lt8.$$
Step 3 - argument of $$\log_{3}$$ must be positive
Let $$z=\log_{7}(y)$$. For $$\log_{3}(z)$$ to be positive we require $$z\gt1$$ (because base $$3\gt1$$). Thus
$$\log_{7}\!\bigl(8-\log_{2}(x^{2}+4x+5)\bigr)\gt1 \;\Longrightarrow\; 8-\log_{2}(x^{2}+4x+5)\gt7.$$
Step 4 - simplifying the last inequality
$$8-\log_{2}(x^{2}+4x+5)\gt7 \;\Longrightarrow\; \log_{2}(x^{2}+4x+5)\lt1 \;\Longrightarrow\; x^{2}+4x+5\lt2.$$
Because $$x^{2}+4x+5=(x+2)^{2}+1$$, the above becomes
$$(x+2)^{2}+1\lt2 \;\Longrightarrow\; (x+2)^{2}\lt1 \;\Longrightarrow\; -1\lt x+2\lt1 \;\Longrightarrow\; -3\lt x\lt-1.$$
Hence the domain of $$f(x)$$ is $$(\alpha,\beta)=(-3,-1).$$ So $$\alpha=-3,\;\beta=-1.$$
Case 2: Domain of $$g(x)=\sin^{-1}\!\left(\dfrac{7x+10}{\,x-2\,}\right)$$
The argument of $$\sin^{-1}$$ must lie in $$[-1,1]$$ and the denominator cannot be zero.
Let $$t=\dfrac{7x+10}{x-2}$$. We need $$-1\le t\le1,\;x\ne2.$$
1) Inequality $$t\le1$$:
$$\dfrac{7x+10}{x-2}\le1 \;\Longrightarrow\; \dfrac{6(x+2)}{x-2}\le0.$$
This holds for $$-2\le x<2.$$
2) Inequality $$t\ge-1$$:
$$\dfrac{7x+10}{x-2}\ge-1 \;\Longrightarrow\; \dfrac{8(x+1)}{x-2}\ge0.$$
This is true for $$x\le-1$$ or $$x>2.$$
3) Intersection of (1) and (2):
$$[-2,2)\;\cap\;(-\infty,-1]\;=\;[-2,-1].$$
The endpoint $$x=-2$$ gives $$t=1$$ and $$x=-1$$ gives $$t=-1,$$ both allowed. Hence the domain of $$g(x)$$ is $$[\gamma,\delta]=[-2,-1]$$ with $$\gamma=-2,\;\delta=-1.$$
Case 3: Required sum
$$\alpha^2+\beta^2+\gamma^2+\delta^2 =(-3)^2+(-1)^2+(-2)^2+(-1)^2 =9+1+4+1 =15.$$
Therefore, $$\alpha^2+\beta^2+\gamma^2+\delta^2=15$$, which matches Option A.
Let $$f : [0:3]\rightarrow A$$ be defined by $$f(x)=2x^{3}-15x^{2}+36x+7$$ and $$g: [0,\infty)\rightarrow B$$ be defined by $$g(x)=\frac{x^{2015}}{x^{2025}+1}$$. If both the functions are onto and $$S=\left\{x \in Z : x \in A or x \in B \right\}$$, then n(S) is equal to:
Set A (Range of $$f(x)$$):
$$f'(x) = 6x^2 - 30x + 36 = 6(x-2)(x-3)$$.
Critical points at $$x=2, 3$$.
$$f(0)=7, f(2)=35, f(3)=34$$. Range $$A = [7, 35]$$.
Set B (Range of $$g(x)$$):
$$g(0)=0$$. As $$x \to \infty, g(x) \to 0$$. Since $$g(x) \geq 0$$, the range starts at $$0$$. The max value (using AM-GM or derivative) is a very small decimal $$< 1$$. Thus, the only integer in $$B$$ is $$\{0\}$$.
Set S: Integers in $$A \cup B$$: $$\{0, 7, 8, \dots, 35\}$$.
Count: $$1$$ (for $$\{0\}$$) $$+ 29$$ (from $$7$$ to $$35$$) = 30
Let $$f(x)$$ be a continuously differentiable function on the interval $$(0, \infty)$$ such that $$f(1) = 2$$ and $$\lim_{t \to x} \frac{t^{10}f(x) - x^{10}f(t)}{t^9 - x^9} = 1$$ for each $$x \gt 0$$. Then, for all $$x \gt 0$$, $$f(x)$$ is equal to
The limit condition is
$$\lim_{t \to x}\;\frac{t^{10}f(x)-x^{10}f(t)}{t^{9}-x^{9}} = 1 \qquad\forall\,x\gt0$$
For fixed $$x$$, treat the numerator and denominator as functions of the variable $$t$$:
• $$g(t)=t^{10}f(x)-x^{10}f(t)$$ with $$g(x)=0$$
• $$h(t)=t^{9}-x^{9}$$ with $$h(x)=0$$
Because both approach $$0$$ as $$t\to x$$, apply L’Hospital’s Rule (differentiate with respect to $$t$$):
$$\lim_{t\to x}\frac{g(t)}{h(t)}
=\frac{g'(x)}{h'(x)}$$
Compute the derivatives:
$$g'(t)=10t^{9}f(x)-x^{10}f'(t)\;\;\Longrightarrow\;\;g'(x)=10x^{9}f(x)-x^{10}f'(x)$$
$$h'(t)=9t^{8}\;\;\Longrightarrow\;\;h'(x)=9x^{8}$$
The limit equals 1, so
$$\frac{10x^{9}f(x)-x^{10}f'(x)}{9x^{8}} = 1$$
Multiply by $$9x^{8}$$:
$$10x^{9}f(x)-x^{10}f'(x)=9x^{8}$$
Divide by $$x^{8}$$:
$$10x\,f(x)-x^{2}f'(x)=9$$
Re-arrange to a first-order linear differential equation:
$$f'(x)-\frac{10}{x}f(x)=-\frac{9}{x^{2}} \quad -(1)$$
Let integrating factor $$I(x)=e^{\int -10/x\,dx}=e^{-10\ln x}=x^{-10}$$.
Multiply $$-(1)$$ by $$x^{-10}$$:
$$x^{-10}f'(x)-\frac{10}{x}x^{-10}f(x)=-9x^{-12}$$
The left side is the derivative of $$x^{-10}f(x)$$:
$$\frac{d}{dx}\bigl(x^{-10}f(x)\bigr)=-9x^{-12}$$
Integrate:
$$x^{-10}f(x)=\int -9x^{-12}\,dx=-9\cdot\frac{x^{-11}}{-11}+C=\frac{9}{11}x^{-11}+C$$
Multiply by $$x^{10}$$ to get $$f(x)$$:
$$f(x)=x^{10}\Bigl(\frac{9}{11}x^{-11}+C\Bigr)
=\frac{9}{11x}+Cx^{10}$$
Use the given value $$f(1)=2$$:
$$2=\frac{9}{11}+C\;\;\Longrightarrow\;\;C=2-\frac{9}{11}=\frac{13}{11}$$
Hence, for all $$x\gt0$$,
$$f(x)=\frac{9}{11x}+\frac{13}{11}x^{10}$$
Option B which is: $$\frac{9}{11x} + \frac{13}{11}x^{10}$$
Let $$S = \{x \in R : (\sqrt{3} + \sqrt{2})^x + (\sqrt{3} - \sqrt{2})^x = 10$$}. Then the number of elements in $$S$$ is:
We need to find the set $$S = \{x \in \mathbb{R} : (\sqrt{3} + \sqrt{2})^x + (\sqrt{3} - \sqrt{2})^x = 10\}$$.
First, note that $$(\sqrt{3} + \sqrt{2})(\sqrt{3} - \sqrt{2}) = 3 - 2 = 1$$, so $$(\sqrt{3} - \sqrt{2}) = \frac{1}{\sqrt{3} + \sqrt{2}}$$ and hence $$(\sqrt{3} - \sqrt{2})^x = (\sqrt{3} + \sqrt{2})^{-x}$$.
Let $$t = (\sqrt{3} + \sqrt{2})^x$$. Since $$\sqrt{3} + \sqrt{2} > 1$$, it follows that $$t > 0$$. Substituting into the given equation gives $$t + \frac{1}{t} = 10$$.
Multiplying both sides by $$t$$ yields $$t^2 + 1 = 10t$$, or $$t^2 - 10t + 1 = 0$$.
Applying the quadratic formula gives $$t = \frac{10 \pm \sqrt{100 - 4}}{2} = \frac{10 \pm \sqrt{96}}{2} = \frac{10 \pm 4\sqrt{6}}{2} = 5 \pm 2\sqrt{6}$$. Both roots are positive since $$2\sqrt{6} \approx 4.899$$, so $$t_1 = 5 + 2\sqrt{6} > 0$$ and $$t_2 = 5 - 2\sqrt{6} \approx 0.101 > 0$$.
Observe that $$5 + 2\sqrt{6} = (\sqrt{3} + \sqrt{2})^2$$, because $$(\sqrt{3} + \sqrt{2})^2 = 3 + 2\sqrt{6} + 2 = 5 + 2\sqrt{6}$$; similarly, $$5 - 2\sqrt{6} = (\sqrt{3} - \sqrt{2})^2 = (\sqrt{3} + \sqrt{2})^{-2}$$. Hence, if $$(\sqrt{3} + \sqrt{2})^x = 5 + 2\sqrt{6}$$ then $$x = 2$$, and if $$(\sqrt{3} + \sqrt{2})^x = 5 - 2\sqrt{6}$$ then $$x = -2$$.
Therefore, $$S = \{-2, 2\}$$, which contains 2 elements. The correct answer is 2 (Option C).
Let $$A$$ and $$B$$ be two finite sets with $$m$$ and $$n$$ elements respectively. The total number of subsets of the set $$A$$ is 56 more than the total number of subsets of $$B$$. Then the distance of the point $$P(m, n)$$ from the point $$Q(-2, -3)$$ is
The number of subsets for a set with $$k$$ elements is $$2^k$$.
We are given $$2^m - 2^n = 56$$.
Factor out $$2^n$$: $$2^n(2^{m-n} - 1) = 56$$.
Prime factorize $$56 = 8 \times 7 = 2^3 \times (2^3 - 1)$$.
Comparing terms, $$n = 3$$ and $$m-n = 3 \Rightarrow m = 6$$. So, $$P$$ is $$(6, 3)$$.
Use the distance formula:
$$\text{Distance} = \sqrt{(6 - (-2))^2 + (3 - (-3))^2} = \sqrt{8^2 + 6^2} = \sqrt{100} = 10$$
Let $$f(x) = \begin{cases} x - 1, & x \text{ is even} \\ 2x, & x \text{ is odd} \end{cases}, \ x \in \mathbb{N}$$. If for some $$a \in \mathbb{N}$$, $$f(f(f(a))) = 21$$, then $$\lim_{x \rightarrow a^{-}} \left\{ \frac{\vert{}x\vert{}^3}{a} - \left[\frac{x}{a}\right] \right\}$$ where $$[t]$$ denotes the greatest integer less than or equal to $$t$$, is equal to:
$$f(x) = \begin{cases} x - 1; & x = \text{even} \\ 2x; & x = \text{odd} \end{cases}$$
$$f(f(f(a))) = 21$$
Case-1: If $$a = \text{even}$$
$$f(a) = a - 1 = \text{odd}$$
$$f(f(a)) = 2(a - 1) = \text{even}$$
$$f(f(f(a))) = 2a - 3 = 21 \Rightarrow a = 12$$
Case-2: If $$a = \text{odd}$$
$$f(a) = 2a = \text{even}$$
$$f(f(a)) = 2a - 1 = \text{odd}$$
$$f(f(f(a))) = 4a - 2 = 21 \text{ (Not possible)}$$
Hence $$a = 12$$
Now, $$\lim_{x \rightarrow 12^{-}} \left( \frac{\vert{}x\vert{}^3}{12} - \left[\frac{x}{12}\right] \right)$$
$$= \lim_{x \rightarrow 12^{-}} \frac{\vert{}x\vert{}^3}{12} - \lim_{x \rightarrow 12^{-}} \left[\frac{x}{12}\right]$$
$$= 144 - 0$$ $$= 144$$
Let $$[t]$$ be the greatest integer less than or equal to $$t$$. Let $$A$$ be the set of all prime factors of 2310 and $$f : A \rightarrow \mathbb{Z}$$ be the function $$f(x) = \left[\log_2\left(x^2 + \left[\frac{x^3}{5}\right]\right)\right]$$. The number of one-to-one functions from $$A$$ to the range of $$f$$ is
2310 = 2×3×5×7×11. A = {2,3,5,7,11} (5 elements). f(2)=[log₂(4+1)]=[2.32]=2. f(3)=[log₂(9+5)]=[3.81]=3. f(5)=[log₂(25+25)]=[5.64]=5. f(7)=[log₂(49+68)]=[log₂117]=[6.87]=6. f(11)=[log₂(121+266)]=[log₂387]=[8.59]=8. Range={2,3,5,6,8}: 5 elements. One-to-one from 5 to 5: 5!=120.
Option (4): 120.
Let $$A = \{1, 3, 7, 9, 11\}$$ and $$B = \{2, 4, 5, 7, 8, 10, 12\}$$. Then the total number of one-one maps $$f : A \to B$$, such that $$f(1) + f(3) = 14$$, is :
Let the sets be $$A = \{1, 3, 7, 9, 11\}$$ and $$B = \{2, 4, 5, 7, 8, 10, 12\}$$.
We seek one-one maps $$f: A \to B$$ such that $$f(1) + f(3) = 14$$.
Considering ordered pairs from B that sum to 14, we have $$(2,12), (4,10), (7,7)$$, but $$(7,7)$$ is not allowed under a one-one mapping, so the valid pairs are $$(2,12)$$ and $$(4,10)$$.
Each of these pairs yields two assignments for $$f(1)$$ and $$f(3)$$, namely for $$(2,12)$$ the options $$f(1)=2, f(3)=12$$ or $$f(1)=12, f(3)=2$$, and for $$(4,10)$$ the options $$f(1)=4, f(3)=10$$ or $$f(1)=10, f(3)=4$$, giving 4 total assignments.
Since pairs like $$(5,9)$$ and $$(6,8)$$ are invalid because 9 and 6 are not in B, there are no further assignments for $$f(1)$$ and $$f(3)$$ beyond these four.
For each of these assignments, the remaining three elements $$\{7,9,11\}$$ of A must be mapped one-to-one to any three of the remaining five elements of B. The number of such mappings is $$P(5,3) = 5 \times 4 \times 3 = 60$$.
Therefore, the total number of one-one maps satisfying the condition is $$4 \times 60 = 240$$.
The correct answer is Option (2): 240.
If $$f(x) = \begin{cases} 2 + 2x, & -1 \leq x < 0 \\ 1 - \frac{x}{3}, & 0 \leq x \leq 3 \end{cases}$$; $$g(x) = \begin{cases} -x, & -3 \leq x \leq 0 \\ x, & 0 < x \leq 1 \end{cases}$$, then range of $$(f \circ g(x))$$ is
We need to find the range of the composite function $$f \circ g(x) = f(g(x))$$.
Determine the domain and range of $$g(x)$$.
$$g(x) = \begin{cases} -x, & -3 \leq x \leq 0 \\ x, & 0 < x \leq 1 \end{cases}$$
For $$x \in [-3, 0]$$: $$g(x) = -x \in [0, 3]$$
For $$x \in (0, 1]$$: $$g(x) = x \in (0, 1]$$
So the range of $$g$$ is $$[0, 3]$$.
Evaluate $$f(g(x))$$ where $$g(x) \in [0, 3]$$.
Since $$g(x) \in [0, 3]$$, we use the second piece of $$f$$:
$$f(t) = 1 - \frac{t}{3}$$ for $$0 \leq t \leq 3$$
When $$t = 0$$: $$f(0) = 1$$
When $$t = 3$$: $$f(3) = 1 - 1 = 0$$
Since $$f(t) = 1 - t/3$$ is continuous and decreasing on $$[0, 3]$$, its range on this interval is $$[0, 1]$$.
Verify that all values in $$[0, 1]$$ are achieved.
For any $$y \in [0, 1]$$, we need $$t = 3(1-y) \in [0, 3]$$, and we need some $$x$$ in the domain of $$g$$ such that $$g(x) = t$$.
Since $$g$$ maps $$[-3, 0]$$ onto $$[0, 3]$$ (via $$g(x) = -x$$), every value $$t \in [0, 3]$$ is achieved.
Therefore, $$f(g(x))$$ achieves all values in $$[0, 1]$$, including both endpoints.
The range of $$f \circ g(x)$$ is $$[0, 1]$$.
The correct answer is Option (3): $$[0, 1]$$.
If the domain of the function $$\sin^{-1}\left(\frac{3x-22}{2x-19}\right) + \log_e\left(\frac{3x^2-8x+5}{x^2-3x-10}\right)$$ is $$(\alpha, \beta]$$, then $$3\alpha + 10\beta$$ is equal to:
For $$\sin^{-1}(u)$$: $$-1 \le \frac{3x-22}{2x-19} \le 1$$.
o Case 1: $$\frac{3x-22}{2x-19} + 1 \ge 0 \implies \frac{5x-41}{2x-19} \ge 0 \implies x \in (-\infty, 8.2] \cup (9.5, \infty)$$.
o Case 2: $$\frac{3x-22}{2x-19} - 1 \le 0 \implies \frac{x-3}{2x-19} \le 0 \implies x \in [3, 9.5)$$.
Intersection: $$x \in [3, 8.2]$$.
For $$\log(v)$$: $$\frac{(3x-5)(x-1)}{(x-5)(x+2)} > 0$$.
Critical points: $$-2, 1, 5/3, 5$$.
Intervals: $$(-\infty, -2) \cup (1, 5/3) \cup (5, \infty)$$.
Common Domain: Intersect $$[3, 8.2]$$ with the log domain $$\implies x \in (5, 8.2]$$.
$$\alpha = 5, \beta = 8.2 = \frac{41}{5}$$.
Calculate: $$3\alpha + 10\beta = 3(5) + 10(\frac{41}{5}) = 15 + 82 = 97$$.
Let $$f: \mathbb{R} - \left\{ \frac{-1}{2} \right\} \to \mathbb{R}$$ and $$g: \mathbb{R} - \left\{ \frac{-5}{2} \right\} \to \mathbb{R}$$ be defined as $$f(x) = \frac{2x + 3}{2x + 1}$$ and $$g(x) = \frac{|x| + 1}{2x + 5}$$. Then the domain of the function fog is:
The composite function $$f\circ g$$ is defined at a real number $$x$$ when both of the following conditions are satisfied:
• $$g(x)$$ is defined (so $$x$$ lies in the domain of $$g$$).
• $$g(x)$$ lies in the domain of $$f$$ (so $$g(x)\neq -\tfrac12$$, because $$f$$ is not defined at $$x=-\tfrac12$$).
Step 1: Write the individual domains.
• For $$f(x)=\dfrac{2x+3}{2x+1}$$ the denominator must be non-zero, so $$2x+1\neq 0\; \Rightarrow\; x\neq -\tfrac12$$; hence
Domain$$(f)=\mathbb{R}-\left\{-\tfrac12\right\}$$.
• For $$g(x)=\dfrac{|x|+1}{2x+5}$$ the denominator must be non-zero, so $$2x+5\neq 0\; \Rightarrow\; x\neq -\tfrac52$$; hence
Domain$$(g)=\mathbb{R}-\left\{-\tfrac52\right\}$$.
Step 2: Find the values of $$x$$ (if any) for which $$g(x)=-\tfrac12$$, because those would be excluded from the domain of $$f\circ g$$.
Case 1: $$x\ge 0\Rightarrow |x|=x$$.
Equation: $$\frac{x+1}{2x+5}=-\frac12$$.
Cross-multiplying: $$2(x+1)=-(2x+5)\;\Rightarrow\;2x+2=-2x-5\;\Rightarrow\;4x+7=0$$.
This gives $$x=-\tfrac74$$, which is negative, contradicting $$x\ge 0$$. Hence no solution in this case.
Case 2: $$x\lt 0\Rightarrow |x|=-x$$.
Equation: $$\frac{-x+1}{2x+5}=-\frac12$$.
Cross-multiplying: $$2(-x+1)=-(2x+5)\;\Rightarrow\;-2x+2=-2x-5$$.
Adding $$2x$$ to both sides gives $$2=-5$$, which is impossible. Hence no solution in this case either.
Thus $$g(x)$$ never equals $$-\tfrac12$$ for any real $$x$$.
Step 3: Collect the restrictions.
• The only restriction from $$g$$ is $$x\neq -\tfrac52$$.
• There is no additional restriction from $$f$$ because $$g(x)\neq -\tfrac12$$ for every real $$x$$.
Therefore the domain of the composite function $$f\circ g$$ is
$$\mathbb{R}-\left\{-\tfrac52\right\}$$.
Hence the correct option is Option A.
Let $$f(x) = \begin{cases} -a & \text{if } -a \leq x \leq 0 \\ x + a & \text{if } 0 < x \leq a \end{cases}$$ where $$a > 0$$ and $$g(x) = (f(x) - |f(x)|)/2$$. Then the function $$g : [-a, a] \rightarrow [-a, a]$$ is :
$$(g(x)=\frac{f(x)-|f(x)|}{2})$$
$$If(f(x)<0\Rightarrow g(x)=f(x)=-a)$$
$$If(f(x)>0\Rightarrow g(x)=0)$$
So range = ({-a, 0})
→ Not one-one, not onto
Neither one-one nor onto
If $$f(x) = \frac{4x+3}{6x-4}, x \neq \frac{2}{3}$$ and $$(f \circ f)(x) = g(x)$$, where $$g: \mathbb{R} - \left\{\frac{2}{3}\right\} \to \mathbb{R} - \left\{\frac{2}{3}\right\}$$, then $$(g \circ g \circ g)(4)$$ is equal to
$$f(f(x)) = f\left(\frac{4x+3}{6x-4}\right) = \frac{4 \cdot \frac{4x+3}{6x-4} + 3}{6 \cdot \frac{4x+3}{6x-4} - 4}$$
Simplify the numerator:
$$\frac{4(4x+3) + 3(6x-4)}{6x-4} = \frac{16x+12+18x-12}{6x-4} = \frac{34x}{6x-4}$$
Simplify the denominator:
$$\frac{6(4x+3) - 4(6x-4)}{6x-4} = \frac{24x+18-24x+16}{6x-4} = \frac{34}{6x-4}$$
Therefore, $$f(f(x)) = \frac{34x/(6x-4)}{34/(6x-4)} = \frac{34x}{34} = x$$ which means that $$g(x) = f(f(x))$$ is the identity function.
Since $$g$$ is the identity function,
$$(g \circ g \circ g)(4) = g(g(g(4))) = g(g(4)) = g(4) = 4.$$
If the domain of the function $$f(x) = \frac{\sqrt{x^2 - 25}}{4 - x^2} + \log_{10}(x^2 + 2x - 15)$$ is $$(-\infty, \alpha) \cup [\beta, \infty)$$, then $$\alpha^2 + \beta^3$$ is equal to:
$$x \leq -5$$ or $$x \geq 5$$.
$$x^2 \neq 4$$, so $$x \neq \pm 2$$.
Combined with Step 1 ($$|x| \geq 5$$), the condition $$x \neq \pm 2$$ is automatically satisfied.
Requires $$x^2 + 2x - 15 > 0$$ (strictly positive for log).
Factoring: $$(x+5)(x-3) > 0$$.
By interval testing: positive when $$x < -5$$ or $$x > 3$$.
From Step 1: $$x \leq -5$$ or $$x \geq 5$$.
From Step 3: $$x < -5$$ or $$x > 3$$.
Intersection: $$(x \leq -5) \cap (x < -5) = x < -5$$, and $$(x \geq 5) \cap (x > 3) = x \geq 5$$.
Wait: at $$x = -5$$: $$x^2 + 2x - 15 = 25 - 10 - 15 = 0$$, and $$\log(0)$$ is undefined. So $$x = -5$$ is excluded.
Domain: $$(-\infty, -5) \cup [5, \infty)$$.
Comparing with $$(-\infty, \alpha) \cup [\beta, \infty)$$: $$\alpha = -5$$ and $$\beta = 5$$.
$$\alpha^2 + \beta^3 = (-5)^2 + 5^3 = 25 + 125 = 150$$.
The correct answer is Option C: 150.
Let $$f: \mathbb{R} \to \mathbb{R}$$ and $$g: \mathbb{R} \to \mathbb{R}$$ be defined as $$f(x) = \begin{cases} \log_e x, & x \gt 0 \\ e^{-x}, & x \leq 0 \end{cases}$$ and $$g(x) = \begin{cases} x, & x \geq 0 \\ e^x, & x \lt 0 \end{cases}$$. Then, $$g \circ f: \mathbb{R} \to \mathbb{R}$$ is:
$$h(x) = g(f(x))$$.
If $$x > 0$$, $$f(x) = \log_e x$$.
If $$\log_e x \ge 0$$ (i.e., $$x \ge 1$$), $$h(x) = \log_e x$$.
If $$\log_e x < 0$$ (i.e., $$0 < x < 1$$), $$h(x) = e^{\log_e x} = x$$.
If $$x \le 0$$, $$f(x) = e^{-x} \ge 1$$.
Since $$f(x) \ge 1$$, $$h(x) = e^{-x}$$ (using the $$x \ge 0$$ case of $$g(x)$$).
The function values are always $$>0$$. Therefore, it can never reach negative values in the codomain $$\mathbb{R}$$. It is not onto.
Check values: $$h(1/2) = 1/2$$. Also, $$h(x) = e^{-x}$$ for $$x \le 0$$ covers $$[1, \infty)$$. The function is not monotonic and repeats values.
Result: B (neither one-one nor onto).
Let the sum of the maximum and the minimum values of the function $$f(x) = \frac{2x^2-3x+8}{2x^2+3x+8}$$ be $$\frac{m}{n}$$, where gcd(m, n) = 1. Then m + n is equal to:
Let the range of $$f(x)=\dfrac{2x^{2}-3x+8}{2x^{2}+3x+8}$$ be $$\left[f_{\min},\,f_{\max}\right]$$. To find $$f_{\min}$$ and $$f_{\max}$$, set $$f(x)=y$$ and eliminate $$x$$.
$$y=\dfrac{2x^{2}-3x+8}{2x^{2}+3x+8}$$ Cross-multiplying gives $$y\bigl(2x^{2}+3x+8\bigr)=2x^{2}-3x+8$$ $$\Longrightarrow(2-2y)x^{2}+(-3-3y)x+(8-8y)=0$$
Factor the common terms: $$2(1-y)x^{2}-3(1+y)x+8(1-y)=0 \;-(1)$$ Equation $$(1)$$ is quadratic in $$x$$. For real $$x$$, its discriminant must satisfy $$\Delta\ge 0$$.
Coefficients of $$(1)$$ are $$A=2(1-y),\;B=-3(1+y),\;C=8(1-y)$$. Hence $$\Delta=B^{2}-4AC$$ $$\Delta=\bigl[-3(1+y)\bigr]^{2}-4\cdot2(1-y)\cdot8(1-y)$$ $$\Delta=9(1+y)^{2}-64(1-y)^{2}$$
Expand both squares: $$(1+y)^{2}=1+2y+y^{2},\qquad(1-y)^{2}=1-2y+y^{2}$$ $$\therefore\;\Delta=9(1+2y+y^{2})-64(1-2y+y^{2})$$ $$\Delta=9+18y+9y^{2}-64+128y-64y^{2}$$ $$\Delta=-55y^{2}+146y-55$$
For real $$x$$, $$\Delta\ge 0$$, so $$-55y^{2}+146y-55\;\ge\;0$$ Multiply by $$-1$$ (reversing the inequality): $$55y^{2}-146y+55\;\le\;0 \;-(2)$$
Quadratic $$(2)$$ in $$y$$ has roots $$y=\dfrac{146\pm\sqrt{146^{2}-4\cdot55\cdot55}}{2\cdot55}$$ Compute the discriminant: $$146^{2}-4\cdot55\cdot55=21316-12100=9216=96^{2}$$ Thus the roots are $$y_{1}=\dfrac{146-96}{110}=\dfrac{50}{110}=\dfrac{5}{11},\qquad y_{2}=\dfrac{146+96}{110}=\dfrac{242}{110}=\dfrac{11}{5}$$
Because the coefficient $$55$$ in $$(2)$$ is positive, inequality $$(2)$$ holds for $$y$$ lying between the roots. Therefore $$\boxed{\dfrac{5}{11}\;\le\;y\;\le\;\dfrac{11}{5}}$$ Hence $$f_{\min}=\dfrac{5}{11},\qquad f_{\max}=\dfrac{11}{5}$$
The required sum is $$f_{\min}+f_{\max}=\dfrac{5}{11}+\dfrac{11}{5}$$ Take the common denominator $$55$$: $$=\dfrac{25}{55}+\dfrac{121}{55}=\dfrac{146}{55}$$
Here $$m=146,\;n=55$$ with $$\gcd(m,n)=1$$, so $$m+n=146+55=201$$.
The correct option is Option B (201).
The function $$f: \mathbb{R} \rightarrow \mathbb{R}$$, $$f(x) = \frac{x^2 + 2x - 15}{x^2 - 4x + 9}$$, $$x \in \mathbb{R}$$ is
$$f(x) = \frac{x^2+2x-15}{x^2-4x+9}$$. Denominator: discriminant = 16-36 = -20 < 0, always positive.
Check one-one: f(3) = (9+6-15)/(9-12+9) = 0/6 = 0. f(-5) = (25-10-15)/(25+20+9) = 0/54 = 0. Not one-one.
Check onto: Let y = f(x). Then x²+2x-15 = y(x²-4x+9). (1-y)x² + (2+4y)x - (15+9y) = 0.
For real x: D ≥ 0. (2+4y)² + 4(1-y)(15+9y) ≥ 0.
4+16y+16y² + 4(15+9y-15y-9y²) ≥ 0. 4+16y+16y²+60-24y-36y² ≥ 0. -20y²-8y+64 ≥ 0. 20y²+8y-64 ≤ 0.
5y²+2y-16 ≤ 0. Roots: y = (-2±√(4+320))/10 = (-2±18)/10. y ∈ [-2, 8/5].
Range is [-2, 8/5] ≠ ℝ. Not onto.
The correct answer is Option (4): neither one-one nor onto.
If the function $$f: (-\infty, -1] \rightarrow [a, b]$$ defined by $$f(x) = e^{x^3 - 3x + 1}$$ is one-one and onto, then the distance of the point $$P(2b + 4, a + 2)$$ from the line $$x + e^{-3}y = 4$$ is:
Let $$g(x) = x^3 - 3x + 1$$, so $$f(x) = e^{g(x)}$$.
$$g'(x) = 3x^2 - 3 = 3(x-1)(x+1).$$
On $$(-\infty, -1)$$ we have $$g'(x) > 0$$ , so $$g$$ is strictly increasing.
At $$x = -1$$, $$g(-1) = -1 + 3 + 1 = 3$$, giving a local maximum of $$g$$. As $$x \to -\infty$$, $$g(x) \to -\infty$$.
Thus on $$(-\infty, -1]$$, $$g$$ increases from $$-\infty$$ to $$3$$, and consequently $$f(x) = e^{g(x)}$$ increases from $$0$$ to $$e^3$$.
Therefore the range of $$f$$ on this domain is $$(0, e^3]$$, which implies $$a = 0$$ and $$b = e^3$$.
$$P(2b + 4, a + 2) = P(2e^3 + 4, 2).$$
$$x + e^{-3}y - 4 = 0$$.
The distance from a point $$(x_0, y_0)$$ to this line is given by $$\frac{|x_0 + e^{-3}y_0 - 4|}{\sqrt{1 + e^{-6}}}.$$
Substituting $$x_0 = 2e^3 + 4$$ and $$y_0 = 2$$ yields
$$\frac{|2e^3 + 4 + 2e^{-3} - 4|}{\sqrt{1 + e^{-6}}} = \frac{|2e^3 + 2e^{-3}|}{\sqrt{1 + e^{-6}}} = \frac{2(e^3 + e^{-3})}{\sqrt{1 + e^{-6}}} = \frac{2e^{-3}(e^6 + 1)}{e^{-3}\sqrt{e^6 + 1}} = \frac{2(e^6+1)}{\sqrt{e^6+1}} = 2\sqrt{e^6 + 1} = 2\sqrt{1 + e^6}.$$
The function $$f : \mathbb{N} - \{1\} \rightarrow \mathbb{N}$$; defined by $$f(n) =$$ the highest prime factor of $$n$$, is :
$$f : \mathbb{N} - \{1\} \to \mathbb{N}$$ where $$f(n)$$ = highest prime factor of $$n$$.
One-one? No. $$f(4) = 2$$ and $$f(8) = 2$$. Different inputs give the same output.
Onto? We need every natural number to be a highest prime factor of some $$n$$. But $$f(n)$$ is always a prime number, so $$1, 4, 6, 8, ...$$ (non-primes) are never in the range. So not onto.
The function is neither one-one nor onto. The answer corresponds to Option (4).
For the function $$f(x) = \sin x + 3x - \frac{2}{\pi}(x^2 + x)$$, where $$x \in [0, \frac{\pi}{2}]$$, consider the following two statements : (I) $$f$$ is increasing in $$(0, \frac{\pi}{2})$$. (II) $$f'$$ is decreasing in $$(0, \frac{\pi}{2})$$. Between the above two statements,
$$f(x) = \sin x + 3x - \frac{2}{\pi}(x^2 + x)$$ on $$[0, \pi/2]$$.
Statement (I): f is increasing in $$(0, \pi/2)$$.
$$ f'(x) = \cos x + 3 - \frac{2}{\pi}(2x + 1) = \cos x + 3 - \frac{4x}{\pi} - \frac{2}{\pi} $$At $$x = 0$$: $$f'(0) = 1 + 3 - 0 - 2/\pi = 4 - 2/\pi > 0$$.
At $$x = \pi/2$$: $$f'(\pi/2) = 0 + 3 - 2 - 2/\pi = 1 - 2/\pi \approx 1 - 0.637 = 0.363 > 0$$.
Statement (II): f' is decreasing in $$(0, \pi/2)$$.
$$ f''(x) = -\sin x - \frac{4}{\pi} $$Since $$\sin x \geq 0$$ for $$x \in (0, \pi/2)$$: $$f''(x) = -\sin x - 4/\pi < 0$$ for all $$x$$ in this interval.
So $$f'$$ is indeed decreasing. And since $$f'$$ is decreasing and positive at both endpoints, $$f' > 0$$ throughout, confirming f is increasing.
Both statements are true.
The correct answer is Option (4): both (I) and (II) are true.
If $$5f(x) + 4f\left(\frac{1}{x}\right) = x^2 - 2$$, $$\forall x \neq 0$$ and $$y = 9x^2 f(x)$$, then $$y$$ is strictly increasing in:
Given: $$5f(x) + 4f(1/x) = x^2 - 2$$ --- (Eq. 1)
Replace $$x$$ with $$1/x$$: $$5f(1/x) + 4f(x) = \frac{1}{x^2} - 2$$ --- (Eq. 2)
Solve for $$f(x)$$: Multiply (Eq. 1) by 5 and (Eq. 2) by 4, then subtract:
$$25f(x) - 16f(x) = 5(x^2 - 2) - 4(\frac{1}{x^2} - 2)$$
$$9f(x) = 5x^2 - 10 - \frac{4}{x^2} + 8 = 5x^2 - \frac{4}{x^2} - 2$$
Find $$y$$: $$y = 9x^2 f(x) = x^2(5x^2 - \frac{4}{x^2} - 2) = 5x^4 - 2x^2 - 4$$.
Find $$y'$$ for increasing condition: $$y' = 20x^3 - 4x > 0$$.
$$4x(5x^2 - 1) > 0 \implies 4x(\sqrt{5}x - 1)(\sqrt{5}x + 1) > 0$$.
Interval Analysis: Using the number line, the expression is positive in:
$$(-\frac{1}{\sqrt{5}}, 0) \cup (\frac{1}{\sqrt{5}}, \infty)$$
Let $$f(x) = 3\sqrt{x - 2} + \sqrt{4 - x}$$ be a real valued function. If $$\alpha$$ and $$\beta$$ are respectively the minimum and the maximum values of $$f$$, then $$\alpha^2 + 2\beta^2$$ is equal to
f(x)=3√(x-2)+√(4-x). Domain [2,4].
f'(x)=3/(2√(x-2))-1/(2√(4-x))=0. 3√(4-x)=√(x-2). 9(4-x)=x-2. 36-9x=x-2. 10x=38. x=3.8.
f(3.8)=3√1.8+√0.2=3·1.342+0.447=4.472=2√5. β=2√5.
f(2)=0+√2=√2. f(4)=3√2+0=3√2. Check: f(2)=√2≈1.41, f(4)=3√2≈4.24, f(3.8)≈4.47.
α=√2 (minimum), β=2√5 (maximum).
α²+2β²=2+40=42.
The answer is Option (1): 42.
The interval in which the function $$f(x) = x^x, x > 0$$, is strictly increasing is
Differentiate the function.
To differentiate $$y = x^x$$, use logarithmic differentiation:
$$\ln y = x \ln x$$
$$\frac{1}{y} \frac{dy}{dx} = \ln x + x(\frac{1}{x}) = \ln x + 1$$
$$f'(x) = x^x (1 + \ln x)$$
Step 2: Determine where $$f'(x) > 0$$.
Since $$x^x$$ is always positive for $$x > 0$$, the sign depends on $$(1 + \ln x)$$.
$$1 + \ln x > 0$$
$$\ln x > -1$$
$$x > e^{-1} \implies x > \frac{1}{e}$$
Thus, the function is strictly increasing on the interval $$[1/e, \infty)$$.
Correct Option: C ($$[1/e, \infty)$$)
Let $$f : \mathbb{R} \to \mathbb{R}$$ be a function such that $$f(x+y) = f(x) + f(y)$$ for all $$x, y \in \mathbb{R}$$, and $$g : \mathbb{R} \to (0, \infty)$$ be a function such that $$g(x+y) = g(x)g(y)$$ for all $$x, y \in \mathbb{R}$$. If $$f\left(\frac{-3}{5}\right) = 12$$ and $$g\left(\frac{-1}{3}\right) = 2$$, then the value of $$\left(f\left(\frac{1}{4}\right) + g(-2) - 8\right)g(0)$$ is ______.
The function $$f : \mathbb{R} \to \mathbb{R}$$ satisfies the additive rule
$$f(x+y)=f(x)+f(y)\quad\forall\,x,y\in\mathbb{R}.$$
For such a function:
• $$f(0)=f(0+0)=f(0)+f(0)\;\Rightarrow\;f(0)=0$$.
• For any integer $$n$$, $$f(nx)=nf(x)$$ (apply the rule $$n$$ times).
• For any rational $$r=\dfrac{p}{q}$$, $$f(rx)=rf(x)$$ (use the integer result on $$q x$$ and divide).
Given $$f\!\left(-\dfrac35\right)=12$$, we first find $$f\!\left(\dfrac35\right)$$:
$$f\!\left(\dfrac35\right)=-f\!\left(-\dfrac35\right)=-12.$$
Now choose $$x=\dfrac35$$ and a rational multiplier
$$r=\dfrac{1/4}{3/5}=\dfrac{5}{12}$$
so that $$r\,x=\dfrac14$$. Using the rational-multiple rule,
$$f\!\left(\dfrac14\right)=r\,f(x)=\dfrac{5}{12}\,(-12)=-5.$$
The function $$g : \mathbb{R} \to (0,\infty)$$ satisfies the multiplicative rule
$$g(x+y)=g(x)\,g(y)\quad\forall\,x,y\in\mathbb{R}.$$
For such a function:
• $$g(0)=g(0+0)=g(0)^2\;,\;g(0)\gt 0\;\Rightarrow\;g(0)=1.$$
• For any integer $$n$$, $$g(nx)=g(x)^n$$ (apply the rule $$n$$ times).
• Consequently, for rational $$r=\dfrac{p}{q}$$, $$g(rx)=g(x)^r$$ (use the integer result and take roots).
Given $$g\!\left(-\dfrac13\right)=2$$, we obtain $$g\!\left(\dfrac13\right)=\dfrac1{g(-1/3)}=\dfrac12.$$
Write $$-2=6\!\left(-\dfrac13\right)$$. Using the integer-multiple rule,
$$g(-2)=g\!\left(-\dfrac13\right)^{\,6}=2^{6}=64.$$
Now evaluate the required expression:
$$\bigl(f(1/4)+g(-2)-8\bigr)\,g(0)=\bigl((-5)+64-8\bigr)\,(1)=51.$
Hence the value is 51.
Consider the function $$f : \mathbb{R} \to \mathbb{R}$$ defined by $$f(x) = \frac{2x}{\sqrt{1 + 9x^2}}$$. If the composition of $$f$$, $$\underbrace{(f \circ f \circ f \circ \cdots \circ f)}_{10 \text{ times}}(x) = \frac{2^{10}x}{\sqrt{1 + 9\alpha x^2}}$$, then the value of $$\sqrt{3\alpha + 1}$$ is equal to _____
We want to determine $$\sqrt{3\alpha + 1}$$ where $$\underbrace{f \circ f \circ \cdots \circ f}_{10}(x) = \frac{2^{10}x}{\sqrt{1+9\alpha x^2}}$$ and $$f(x) = \frac{2x}{\sqrt{1+9x^2}}\,. $$
To begin, we compute the second iterate by substituting $$f(x)=\frac{2x}{\sqrt{1+9x^2}}$$ into itself, yielding $$f(f(x)) = \frac{2 \cdot \frac{2x}{\sqrt{1+9x^2}}}{\sqrt{1 + 9\bigl(\frac{2x}{\sqrt{1+9x^2}}\bigr)^2}} = \frac{\frac{4x}{\sqrt{1+9x^2}}}{\sqrt{1+\frac{36x^2}{1+9x^2}}} = \frac{4x}{\sqrt{(1+9x^2)+36x^2}} = \frac{4x}{\sqrt{1+45x^2}}\,. $$ Hence $$f^{(2)}(x)=\frac{2^2x}{\sqrt{1+9\cdot 5x^2}}\,. $$
Next we observe a general pattern by defining $$f^{(k)}(x)=\frac{2^k x}{\sqrt{1+9c_k x^2}}\,, $$ where the constants satisfy $$c_1=1$$ and $$c_2=5\,. $$ Applying one more iteration gives $$f^{(k+1)}(x)=f\!\Bigl(\frac{2^k x}{\sqrt{1+9c_k x^2}}\Bigr)=\frac{2^{k+1}x/\sqrt{1+9c_k x^2}}{\sqrt{1+9\cdot\frac{2^{2k}x^2}{1+9c_k x^2}}} = \frac{2^{k+1}x}{\sqrt{1+9c_k x^2+9\cdot2^{2k}x^2}} = \frac{2^{k+1}x}{\sqrt{1+9(c_k+4^k)x^2}}\,. $$ Therefore the recurrence for the coefficients is $$c_{k+1}=c_k+4^k\,. $$
Since this recurrence sums a geometric progression starting from $$c_1=1$$ with ratio $$4\,, $$ we obtain $$c_k=1+4+4^2+\cdots+4^{k-1}=\frac{4^k-1}{3}\,. $$ Checking small values confirms that $$c_1=(4-1)/3=1$$ and $$c_2=(16-1)/3=5\,. $$ Hence for $$k=10$$ we have $$c_{10}=\frac{4^{10}-1}{3}=\frac{1048576-1}{3}=\frac{1048575}{3}=349525\,, $$ so that $$\alpha=c_{10}=349525\,. $$
Finally, substituting this value into the expression under the square root gives $$3\alpha+1=3(349525)+1=1048575+1=1048576=4^{10}=2^{20}\,, $$ and therefore $$\sqrt{3\alpha+1}=\sqrt{2^{20}}=2^{10}=1024\,. $$
Thus, the desired value is 1024.
Let $$A = \{(x, y) : 2x + 3y = 23, x, y \in \mathbb{N}\}$$ and $$B = \{x : (x, y) \in A\}$$. Then the number of one-one functions from $$A$$ to $$B$$ is equal to ________
We need to find natural number pairs $$(x, y)$$ that satisfy $$2x + 3y = 23$$. Since $$3y$$ must be odd (because $$23$$ is odd and $$2x$$ is even), $$y$$ must be odd.
• If $$y=1: 2x + 3 = 23 \implies 2x = 20 \implies x = 10$$. Pair: $$(10, 1)$$
• If $$y=3: 2x + 9 = 23 \implies 2x = 14 \implies x = 7$$. Pair: $$(7, 3)$$
• If $$y=5: 2x + 15 = 23 \implies 2x = 8 \implies x = 4$$. Pair: $$(4, 5)$$
• If $$y=7: 2x + 21 = 23 \implies 2x = 2 \implies x = 1$$. Pair: $$(1, 7)$$
• If $$y=9: 2x + 27 = 23$$ (No natural number solution).
So, $$A = \{(10, 1), (7, 3), (4, 5), (1, 7)\}$$. The number of elements $$n(A) = 4$$.
Finding the elements of Set $$B$$
$$B$$ consists of the $$x$$-coordinates from $$A$$.
$$B = \{10, 7, 4, 1\}$$. The number of elements $$n(B) = 4$$.
Calculating One-One Functions
A one-one function (injection) from a set of size $$n$$ to a set of size $$n$$ is simply a permutation of the elements.
$$\text{Number of functions} = n! = 4! = 4 \times 3 \times 2 \times 1 = 24$$
If $$S = \{a \in \mathbb{R} : |2a - 1| = 3[a] + 2\{a\}\}$$, where $$[t]$$ denotes the greatest integer less than or equal to $$t$$ and $$\{t\}$$ represents the fractional part of $$t$$, then $$72\sum_{a \in S} a$$ is equal to ______
$$a = [a] + \{a\}$$. Let $$[a] = n$$ and $$\{a\} = f$$, where $$f \in [0, 1)$$.
Equation: $$|2(n+f) - 1| = 3n + 2f$$.
Case 1: $$2a - 1 \ge 0 \implies a \ge 1/2$$
$$2n + 2f - 1 = 3n + 2f \implies n = -1$$.
Since $$a = n+f = -1+f$$, the max value is $$<0$$, which contradicts $$a \ge 1/2$$. No solution.
Case 2: $$2a - 1 < 0 \implies a < 1/2$$
$$-(2n + 2f - 1) = 3n + 2f \implies 1 - 2n - 2f = 3n + 2f \implies 4f = 1 - 5n$$.
Since $$0 \le f < 1$$, then $$0 \le \frac{1-5n}{4} < 1$$.
• $$1-5n < 4 \implies -3 < 5n \implies n > -0.6$$
• $$1-5n \ge 0 \implies 5n \le 1 \implies n \le 0.2$$
The only integer $$n$$ in this range is $$n = 0$$.
If $$n = 0$$, $$4f = 1 \implies f = 1/4$$.
$$a = 0 + 1/4 = 1/4$$.
Sum of $$a \in S$$ is $$1/4$$.
$$72 \times (1/4) = 18$$.
Let $$S = (0, 1) \cup (1, 2) \cup (3, 4)$$ and $$T = \{0, 1, 2, 3\}$$. Then which of the following statements is(are) true?
Let $$S = (0,1)\cup(1,2)\cup(3,4)$$ and $$T=\{0,1,2,3\}$$.
The set $$S$$ is the union of three open intervals, so it contains uncountably many real numbers (cardinality of the continuum). The set $$T$$ is finite with $$|T|=4$$.
Option A - “There are infinitely many functions from $$S$$ to $$T$$”.
For an arbitrary function $$f:S\rightarrow T$$ we can (independently) choose any of the four values of $$T$$ for every element of $$S$$.
Hence the total number of such functions is $$4^{|S|}$$.
Since $$|S|$$ is uncountable, $$4^{|S|}$$ is also uncountable, in particular infinite.
Therefore Option A is true.
Option B - “There are infinitely many strictly increasing functions from $$S$$ to $$T$$”.
A strictly increasing function satisfies $$x_1\lt x_2\;\Rightarrow\;f(x_1)\lt f(x_2)$$, so it is injective.
Because $$S$$ is infinite while $$T$$ has only four elements, no injective function from $$S$$ to $$T$$ can exist.
Thus there is not even one (let alone infinitely many) strictly increasing function.
Option B is false.
Option C - “The number of continuous functions from $$S$$ to $$T$$ is at most 120”.
The three components $$(0,1),\,(1,2),\,(3,4)$$ of $$S$$ are connected sets (intervals).
The image of a connected set under a continuous function is also connected.
The only connected subsets of the discrete set $$T=\{0,1,2,3\}$$ are its singletons.
Hence a continuous function $$f:S\rightarrow T$$ must be constant on each of the three intervals:
$$f(x)=a\;\text{on }(0,1),\qquad f(x)=b\;\text{on }(1,2),\qquad f(x)=c\;\text{on }(3,4),$$
where $$a,b,c\in T$$. Thus a continuous function is completely determined by the ordered triple $$(a,b,c)\in T^3$$. The total number of such triples is $$|T|^3 = 4^3 = 64\le 120$$. Therefore Option C is true.
Option D - “Every continuous function from $$S$$ to $$T$$ is differentiable”.
As shown above, every continuous $$f$$ is constant on each open interval.
A constant function on an open interval is differentiable everywhere inside that interval with derivative $$0$$.
The points $$1,2,3$$ (where the function would jump) are not contained in $$S$$, so differentiability there is irrelevant.
Consequently every continuous $$f:S\rightarrow T$$ is differentiable at every point of its domain.
Option D is true.
Hence the correct statements are:
Option A, Option C, Option D.
Which of the following statements is a tautology?
We need to determine which of the given statements is a tautology (always true regardless of the truth values of $$p$$ and $$q$$).
Option A: $$p \to (p \wedge (p \to q))$$
When $$p = T, q = F$$: $$p \to q = F$$, so $$p \wedge F = F$$, and $$T \to F = F$$. Not a tautology.
Option B: $$(p \wedge q) \to (\neg p \to q)$$
Let us check all cases:
$$p = T, q = T$$: $$(T \wedge T) \to (F \to T) = T \to T = T$$ ✓
$$p = T, q = F$$: $$(T \wedge F) \to (F \to F) = F \to T = T$$ ✓
$$p = F, q = T$$: $$(F \wedge T) \to (T \to T) = F \to T = T$$ ✓
$$p = F, q = F$$: $$(F \wedge F) \to (T \to F) = F \to F = T$$ ✓
All cases give TRUE. This is a tautology!
Option C: $$(p \wedge (p \to q)) \to \neg q$$
When $$p = T, q = T$$: $$(T \wedge T) \to F = T \to F = F$$. Not a tautology.
Option D: $$p \vee (p \wedge q)$$
When $$p = F, q = F$$: $$F \vee F = F$$. Not a tautology.
The correct answer is Option B: $$(p \wedge q) \to (\neg p \to q)$$.
Consider:
S1: $$p \Rightarrow q \lor p \land \sim q$$ is a tautology.
S2: $$\sim p \Rightarrow \sim q \land \sim p \lor q$$ is a contradiction.
Then
We need to check whether S1 is a tautology and S2 is a contradiction.
$$p \Rightarrow (q \lor p) \land (\sim q)$$. Actually, let us parse with standard precedence. $$\land$$ binds tighter than $$\lor$$, and $$\Rightarrow$$ has the lowest precedence. So the expression is:
$$p \Rightarrow (q \lor (p \land \sim q))$$
Let us evaluate using a truth table approach. When $$p = T, q = T$$, the right-hand side is $$T \lor (T \land F) = T \lor F = T$$, so $$T \Rightarrow T = T$$; when $$p = T, q = F$$, the right-hand side is $$F \lor (T \land T) = F \lor T = T$$, so $$T \Rightarrow T = T$$; when $$p = F, q = T$$, a false premise implies anything giving $$T$$; and when $$p = F, q = F$$, again a false premise implies anything giving $$T$$.
S1 is TRUE for all truth values, so S1 is a tautology. Statement S1 is correct.
$$\sim p \Rightarrow (\sim q \land \sim p) \lor q$$, which parses as $$\sim p \Rightarrow ((\sim q \land \sim p) \lor q)$$.
When $$p = T$$ (so $$\sim p = F$$), a false premise implies anything, giving $$T$$; when $$p = F, q = T$$ (so $$\sim p = T$$), the right-hand side is $$(F \land T) \lor T = F \lor T = T$$, so $$T \Rightarrow T = T$$; when $$p = F, q = F$$ (so $$\sim p = T$$), the right-hand side is $$(T \land T) \lor F = T \lor F = T$$, so $$T \Rightarrow T = T$$.
S2 is TRUE for all truth values, so S2 is also a tautology and not a contradiction, so the claim that S2 is a contradiction is wrong. Therefore, S1 is correct (it is a tautology), but S2 is incorrect (it is actually a tautology rather than a contradiction), and the correct answer is Option 4, for which only S1 is correct.
Let $$\triangle, \nabla \in \{\wedge, \vee\}$$ be such that $$(p \to q) \triangle (p \nabla q)$$ is a tautology. Then
We need to find $$\triangle, \nabla \in \{\wedge, \vee\}$$ such that $$(p \to q) \triangle (p \nabla q)$$ is a tautology.
Recall that $$p \to q \equiv \neg p \vee q$$.
Test all four combinations.
Case 1: $$\triangle = \vee, \nabla = \vee$$:
$$(\neg p \vee q) \vee (p \vee q) = \neg p \vee p \vee q = \text{T} \vee q = \text{T}$$
This is a tautology.
Case 2: $$\triangle = \vee, \nabla = \wedge$$:
$$(\neg p \vee q) \vee (p \wedge q)$$
When $$p = \text{T}, q = \text{F}$$: $$(\text{F} \vee \text{F}) \vee (\text{T} \wedge \text{F}) = \text{F} \vee \text{F} = \text{F}$$. Not a tautology.
Case 3: $$\triangle = \wedge, \nabla = \vee$$:
$$(\neg p \vee q) \wedge (p \vee q) = q$$
When $$q = \text{F}$$, the expression is $$\text{F}$$. Not a tautology.
Case 4: $$\triangle = \wedge, \nabla = \wedge$$:
$$(\neg p \vee q) \wedge (p \wedge q)$$
When $$p = \text{F}, q = \text{F}$$: $$\text{T} \wedge \text{F} = \text{F}$$. Not a tautology.
Conclusion.
Only $$\triangle = \vee, \nabla = \vee$$ gives a tautology.
The correct answer is Option C: $$\triangle = \vee, \nabla = \vee$$.
The compound statement $$(\sim(P \wedge Q)) \vee ((\sim P) \wedge Q) \Rightarrow ((\sim P) \wedge (\sim Q))$$ is equivalent to
The statement $$B \Rightarrow ((\neg A) \vee B)$$ is not equivalent to:
The statement $$B \Rightarrow ((\neg A) \vee B)$$ simplifies as follows: $$B \Rightarrow (\neg A \vee B) \equiv \neg B \vee (\neg A \vee B) \equiv \neg A \vee (\neg B \vee B) \equiv \neg A \vee T \equiv T.$$ Thus the given statement is a tautology (always true), and we need to find which option is not a tautology.
In Option A, $$B \Rightarrow (A \Rightarrow B) = \neg B \vee (\neg A \vee B) = \neg A \vee \neg B \vee B = \neg A \vee T = T,$$ which is a tautology and therefore equivalent to the given statement.
For Option B, $$A \Rightarrow (A \Leftrightarrow B) = \neg A \vee (A \Leftrightarrow B).$$ When $$A = T, B = F$$, then $$\neg A = F$$ and $$A \Leftrightarrow B = F,$$ so the expression evaluates to $$F \vee F = F.$$ Since this is not always true, Option B is not a tautology and thus is not equivalent to the given statement.
In Option C, $$A \Rightarrow ((\neg A) \Rightarrow B) = \neg A \vee (A \vee B) = (\neg A \vee A) \vee B = T \vee B = T,$$ giving a tautology equivalent to the given statement.
Option D yields $$B \Rightarrow ((\neg A) \Rightarrow B) = \neg B \vee (A \vee B) = A \vee (\neg B \vee B) = A \vee T = T,$$ also a tautology equivalent to the given statement.
Therefore, the only statement not equivalent to the given expression is Option B: $$A \Rightarrow (A \Leftrightarrow B).$$
The statement $$(p \wedge (\sim q)) \Rightarrow (p \Rightarrow (\sim q))$$ is
We need to determine the nature of the statement $$(p \wedge (\sim q)) \Rightarrow (p \Rightarrow (\sim q))$$.
First, simplify $$p \Rightarrow (\sim q) = (\sim p) \vee (\sim q)$$.
So the statement becomes:
$$(p \wedge \sim q) \Rightarrow (\sim p \vee \sim q)$$
$$= \sim(p \wedge \sim q) \vee (\sim p \vee \sim q)$$
$$= (\sim p \vee q) \vee (\sim p \vee \sim q)$$
$$= \sim p \vee q \vee \sim q$$
$$= \sim p \vee T$$
$$= T$$
Since the expression always evaluates to True regardless of the truth values of $$p$$ and $$q$$, this is a tautology.
The answer is Option B: a tautology.
Consider the following statements:
$$P$$: I have fever
$$Q$$: I will not take medicine
$$R$$: I will take rest
The statement "If I have fever, then I will take medicine and I will take rest" is equivalent to:
$$P$$: I have fever, $$Q$$: I will not take medicine, $$R$$: I will take rest.
"If I have fever, then I will take medicine and I will take rest."
"I will take medicine" = $$\sim Q$$ (negation of "I will not take medicine").
So the statement is: $$P \to (\sim Q \wedge R)$$.
$$\equiv \sim P \vee (\sim Q \wedge R)$$
$$\equiv (\sim P \vee \sim Q) \wedge (\sim P \vee R)$$
This matches option 1: $$((\neg P) \vee \neg Q) \wedge ((\neg P) \vee R)$$.
Statement $$(P \Rightarrow Q) \wedge (R \Rightarrow Q)$$ is logically equivalent to
We need to simplify $$(P \Rightarrow Q) \wedge (R \Rightarrow Q)$$.
Using the equivalence $$P \Rightarrow Q \equiv \neg P \vee Q$$:
$$ (P \Rightarrow Q) \wedge (R \Rightarrow Q) = (\neg P \vee Q) \wedge (\neg R \vee Q) $$
By the distributive law (factoring out $$Q$$):
$$ = Q \vee (\neg P \wedge \neg R) $$
By De Morgan's law: $$\neg P \wedge \neg R = \neg(P \vee R)$$
$$ = Q \vee \neg(P \vee R) = \neg(P \vee R) \vee Q $$
This is the implication form:
$$ = (P \vee R) \Rightarrow Q $$
The correct answer is $$(P \vee R) \Rightarrow Q$$.
The negation of the expression $$q \vee ((\sim q) \wedge p)$$ is equivalent to
We need to find the negation of $$q \vee ((\sim q) \wedge p)$$.
First, let us simplify the expression using the distributive law:
$$ q \vee ((\sim q) \wedge p) = (q \vee \sim q) \wedge (q \vee p) $$
Since $$q \vee \sim q = T$$ (tautology):
$$ q \vee ((\sim q) \wedge p) = T \wedge (q \vee p) = q \vee p $$
Now, the negation is:
$$ \sim(q \vee p) = (\sim q) \wedge (\sim p) = (\sim p) \wedge (\sim q) $$
This follows from De Morgan's law: $$\sim(A \vee B) = (\sim A) \wedge (\sim B)$$.
Therefore, the negation is $$(\sim p) \wedge (\sim q)$$.
The negation of the statement $$p \vee q \wedge q \vee \sim r$$ is
First, let's clarify the precedence in the expression. Assuming the standard form $$(p \lor q) \land (q \lor \sim r)$$, we apply De Morgan's Laws:
- Negate the entire expression: $$\sim [(p \lor q) \land (q \lor \sim r)]$$
- Distribute the negation: $$[\sim (p \lor q)] \lor [\sim (q \lor \sim r)]$$
- Simplify: $$(\sim p \land \sim q) \lor (\sim q \land r)$$
- Factor out $$\sim q$$ using the distributive property: $$(\sim p \lor r) \land \sim q$$
Correct Option: (B)
The relation $$R = \{(a, b): \gcd(a, b) = 1, 2a \neq b, a, b \in \mathbb{Z}\}$$ is:
We analyze the relation $$R = \{(a,b) : \gcd(a,b) = 1, 2a \neq b, a, b \in \mathbb{Z}\}$$.
Reflexive?
For reflexivity, we need $$(a, a) \in R$$ for all $$a \in \mathbb{Z}$$. This requires $$\gcd(a, a) = 1$$ and $$2a \neq a$$.
$$\gcd(a, a) = |a|$$, which equals 1 only when $$a = \pm 1$$. For $$a = 2$$: $$\gcd(2,2) = 2 \neq 1$$. So $$(2, 2) \notin R$$.
Therefore, R is NOT reflexive.
Symmetric?
For symmetry, if $$(a, b) \in R$$, we need $$(b, a) \in R$$. We need $$\gcd(b, a) = 1$$ (same as $$\gcd(a, b) = 1$$, so this holds) AND $$2b \neq a$$.
Consider $$(1, 2)$$: $$\gcd(1, 2) = 1$$ and $$2(1) = 2 = b$$, so $$(1, 2) \notin R$$ (fails $$2a \neq b$$).
Consider $$(2, 1)$$: $$\gcd(2, 1) = 1$$ and $$2(2) = 4 \neq 1$$, so $$(2, 1) \in R$$.
But we need the reverse: $$(1, 2)$$. We showed $$(1, 2) \notin R$$.
So $$(2, 1) \in R$$ but $$(1, 2) \notin R$$. Therefore, R is NOT symmetric.
Transitive?
For transitivity, if $$(a, b) \in R$$ and $$(b, c) \in R$$, we need $$(a, c) \in R$$.
Consider $$(3, 2)$$: $$\gcd(3, 2) = 1$$, $$2(3) = 6 \neq 2$$. So $$(3, 2) \in R$$.
Consider $$(2, 3)$$: $$\gcd(2, 3) = 1$$, $$2(2) = 4 \neq 3$$. So $$(2, 3) \in R$$.
Now check $$(3, 3)$$: $$\gcd(3, 3) = 3 \neq 1$$. So $$(3, 3) \notin R$$.
We have $$(3, 2) \in R$$ and $$(2, 3) \in R$$ but $$(3, 3) \notin R$$. Therefore, R is NOT transitive.
The correct answer is Option 4: neither symmetric nor transitive.
Among the statements
(S1): $$(p \Rightarrow q) \lor ((\sim p) \wedge q)$$ is a tautology
(S2): $$(q \Rightarrow p) \Rightarrow ((\sim p) \wedge q)$$ is a contradiction
We begin by determining which of the two statements is true.
First consider the expression $$(p \Rightarrow q) \lor (\lnot p \wedge q)$$ and check whether it is a tautology. Recall that $$p \Rightarrow q \equiv \lnot p \lor q$$. Hence
$$ S1 = (\lnot p \lor q) \lor (\lnot p \wedge q) = \lnot p \lor q $$since $$\lnot p \wedge q$$ is absorbed by $$\lnot p \lor q$$. Testing $$p = T, q = F$$ gives $$\lnot T \lor F = F$$, so this expression is not always true and therefore S1 fails to be a tautology.
Next examine the expression $$(q \Rightarrow p) \Rightarrow (\lnot p \wedge q)$$ to see if it is a contradiction. Noting that $$q \Rightarrow p \equiv \lnot q \lor p$$, we find
$$ S2 = \lnot(\lnot q \lor p) \lor (\lnot p \wedge q) = (q \wedge \lnot p) \lor (\lnot p \wedge q) = \lnot p \wedge q $$and testing $$p = F, q = T$$ yields $$\lnot F \wedge T = T$$. Since the expression can be true, S2 is not a contradiction.
For completeness, the following truth table verifies the values of S1 and S2 under all assignments of $$p$$ and $$q$$:
| $$p$$ | $$q$$ | S1 expression | S2 expression |
| T | T | T | F |
| T | F | F | F |
| F | T | T | T |
| F | F | T | F |
Since S1 is not a tautology (it fails when $$p = T, q = F$$) and S2 is not a contradiction (it holds when $$p = F, q = T$$), neither statement is true.
The correct answer is Option A: Neither (S1) nor (S2) is True.
Among the statements:
S1: $$p \vee q \Rightarrow r \Leftrightarrow p \Rightarrow r$$
S2: $$p \vee q \Rightarrow r \Leftrightarrow p \Rightarrow r \vee q \Rightarrow r$$
Step 1: Understand the Logical Equivalence Rules
The standard logical identity for an implication with a disjunction (OR) in its antecedent is given by:
$$(p \vee q) \Rightarrow r \equiv (p \Rightarrow r) \wedge (q \Rightarrow r)$$
Step 2: Analyze Statement S1
$$S1: ((p \vee q) \Rightarrow r) \Leftrightarrow (p \Rightarrow r)$$
Let us construct a counterexample using truth values to see if this is a tautology:
- Let $$p = \text{False}$$
- Let $$q = \text{True}$$
- Let $$r = \text{False}$$
Evaluate LHS: $$(p \vee q) \Rightarrow r$$
- $$p \vee q = \text{False} \vee \text{True} = \text{True}$$
- $$\text{True} \Rightarrow \text{False} = \text{False}$$
Evaluate RHS: $$p \Rightarrow r$$
- $$\text{False} \Rightarrow \text{False} = \text{True}$$
Since $$\text{LHS} = \text{False}$$ and $$\text{RHS} = \text{True}$$, their bi-conditional equivalence ($$\Leftrightarrow$$) evaluates to $$\text{False}$$.
Therefore, $$S1$$ is not a tautology.
Step 3: Analyze Statement S2
$$S2: ((p \vee q) \Rightarrow r) \Leftrightarrow ((p \Rightarrow r) \vee (q \Rightarrow r))$$
Using our known logical identity from Step 1, the true distribution rule uses an AND ($$\wedge$$) operator, not an OR ($$\vee$$) operator. Let us test with another counterexample:
- Let $$p = \text{True}$$
- Let $$q = \text{False}$$
- Let $$r = \text{False}$$
Evaluate LHS: $$(p \vee q) \Rightarrow r$$
- $$p \vee q = \text{True} \vee \text{False} = \text{True}$$
- $$\text{True} \Rightarrow \text{False} = \text{False}$$
Evaluate RHS: $$(p \Rightarrow r) \vee (q \Rightarrow r)$$
- $$p \Rightarrow r = \text{True} \Rightarrow \text{False} = \text{False}$$
- $$q \Rightarrow r = \text{False} \Rightarrow \text{False} = \text{True}$$
- $$\text{False} \vee \text{True} = \text{True}$$
Since $$\text{LHS} = \text{False}$$ and $$\text{RHS} = \text{True}$$, their bi-conditional equivalence ($$\Leftrightarrow$$) evaluates to $$\text{False}$$.
Therefore, $$S2$$ is also not a tautology.
Conclusion:
Neither (S1) nor (S2) is a tautology.
If $$p, q$$ and $$r$$ are three propositions, then which of the following combination of truth values of $$p$$, $$q$$ and $$r$$ makes the logical expression $$\{(p \vee q) \wedge ((\neg p) \vee r)\} \to ((\neg q) \vee r)$$ false?
To determine the truth values of $$p$$, $$q$$, and $$r$$ that make the logical expression false, let's analyze the implication.
The given expression is:
$$\{(p \lor q) \land (\neg p \lor r)\} \to (\neg q \lor r)$$
Let the premise be $$A = (p \lor q) \land (\neg p \lor r)$$and the conclusion be $$B = \neg q \lor r$$.
The expression is of the form $$A \to B$$.
An implication $$A \to B$$ is false if and only if the premise $$A$$ is True and the conclusion $$B$$ is False.
Step 1: Make the ($$B$$) False
We need $$B = \neg q \lor r$$ to be False.
For a logical OR ($$\lor$$) to be false, both of its components must be false.
$$\neg q$$ must be False $$ \implies $$q is True
$$r$$ must be False $$ \implies$$ r is False
So, we have established that $$q = True $$ and $$r = False$$.
Step 2: Ensure the premise ($$A$$) is True
We need $$A = (p \lor q) \land (\neg p \lor r)$$ to be True.
Substitute the known values ($$q = \text{True}$$, $$r = \text{False}$$) into the premise:
$$p \lor q = p \lor \text{True} = \text{True}$$(since $$q$$ is True, the OR statement is True regardless of $$p$$)
$$\neg p \lor r = \neg p \lor \text{False} = \neg p$$
For the premise $$A$$ to be True, both parts of the AND ($$\land$$) statement must be True.
$$\text{True} \land \neg p$$ must be True.
This means $$\neg p$$ must be True, which implies p is False .
Conclusion
The combination of truth values that makes the given logical expression false is:
$$p = \text{False}$$
$$q = \text{True}$$
$$r = \text{False}$$
The converse of $$((-p) \wedge q) \Rightarrow r$$ is
We need to find the converse of $$((\sim p) \wedge q) \Rightarrow r$$.
Recall the definition of converse.
The converse of $$P \Rightarrow Q$$ is $$Q \Rightarrow P$$.
Apply to the given statement.
Here $$P = (\sim p) \wedge q$$ and $$Q = r$$.
The converse is: $$r \Rightarrow ((\sim p) \wedge q)$$.
Check the options.
Option C states: $$(\sim r) \Rightarrow ((\sim p) \wedge q)$$. This is the inverse, not the converse.
Option D states: $$(p \vee (\sim q)) \Rightarrow (\sim r)$$. This is the contrapositive of the converse.
let me re-examine. The converse of $$(\sim p \wedge q) \Rightarrow r$$ is $$r \Rightarrow (\sim p \wedge q)$$.
Looking at the options more carefully:
Option C: $$(\sim r) \Rightarrow ((\sim p) \wedge q)$$ — this is the inverse (negating both sides of original).
None of the options directly states $$r \Rightarrow (\sim p \wedge q)$$. Let me re-read the options.
The answer given is Option D: $$(p \vee (\sim q)) \Rightarrow (\sim r)$$.
This is actually the contrapositive of the converse. The converse is $$r \Rightarrow (\sim p \wedge q)$$. Its contrapositive is $$\sim(\sim p \wedge q) \Rightarrow \sim r$$, i.e., $$(p \vee \sim q) \Rightarrow \sim r$$.
Since a statement and its contrapositive are logically equivalent, Option D is equivalent to the converse.
The correct answer is Option D.
For $$x \in \mathbb{R}$$, two real valued functions $$f(x)$$ and $$g(x)$$ are such that, $$g(x) = \sqrt{x} + 1$$ and $$fog(x) = x + 3 - \sqrt{x}$$. Then $$f(0)$$ is equal to
Given $$g(x) = \sqrt{x} + 1$$ and $$f \circ g(x) = x + 3 - \sqrt{x}$$.
Express $$f$$ in terms of a new variable.
Let $$t = g(x) = \sqrt{x} + 1$$, so $$\sqrt{x} = t - 1$$ and $$x = (t - 1)^2$$.
Find $$f(t)$$.
$$f(t) = f(g(x)) = x + 3 - \sqrt{x} = (t-1)^2 + 3 - (t-1)$$
$$= t^2 - 2t + 1 + 3 - t + 1 = t^2 - 3t + 5$$
Find $$f(0)$$.
$$f(0) = 0 - 0 + 5 = 5$$
The answer is Option B: $$5$$.
Let $$f : \mathbb{R} \to \mathbb{R}$$ be a function defined by $$f(x) = \log_{\sqrt{m}} \{\sqrt{2}(\sin x - \cos x) + m - 2\}$$, for some $$m$$, such that the range of $$f$$ is $$[0, 2]$$. Then the value of $$m$$ is _____.
We want to find $$m$$ such that $$f(x) = \log_{\sqrt{m}}\{\sqrt{2}(\sin x - \cos x) + m - 2\}$$ has range $$[0, 2]$$. Define $$u = \sqrt{2}(\sin x - \cos x) = 2\sin(x - \pi/4)$$. Since $$\sin(x - \pi/4)\in[-1,1]$$, the range of $$u$$ is $$[-2,2]$$. Therefore the argument of the logarithm is $$g(x) = u + m - 2\in[m-4,m]$$.
For $$f(x) = \log_{\sqrt{m}}(g(x))$$ to have range $$[0,2]$$, its maximum value must satisfy $$\log_{\sqrt{m}}(m) = \frac{\log m}{\log\sqrt{m}} = 2$$, which holds for any valid $$m$$. Its minimum value must satisfy $$\log_{\sqrt{m}}(m-4) = 0$$, implying $$m-4 = 1$$ and hence $$m = 5$$.
With $$m = 5$$ the argument ranges over $$[1,5]$$, so $$f(x)$$ ranges over $$[\log_{\sqrt{5}}1,\;\log_{\sqrt{5}}5] = [0,2]$$. Thus the required value is $$m = 5$$, corresponding to Option 1.
Let $$p$$ and $$q$$ be two statements. Then $$\sim(p \wedge (p \to \sim q))$$ is equivalent to
We need to simplify $$\sim(p \wedge (p \to \sim q))$$.
First, recall that $$p \to \sim q \equiv \sim p \vee \sim q$$.
So: $$p \wedge (p \to \sim q) \equiv p \wedge (\sim p \vee \sim q)$$
Using distribution: $$= (p \wedge \sim p) \vee (p \wedge \sim q)$$
Since $$p \wedge \sim p$$ is always false (contradiction):
$$= F \vee (p \wedge \sim q) = p \wedge \sim q$$
Therefore: $$\sim(p \wedge (p \to \sim q)) = \sim(p \wedge \sim q)$$
By De Morgan's law: $$= \sim p \vee q$$
$$= (\sim p) \vee q$$
The correct answer is Option 3: $$(\sim p) \vee q$$.
The number of values of $$r \in \{p, q, \sim p, \sim q\}$$ for which $$((p \wedge q) \Rightarrow (r \vee q)) \wedge ((p \wedge r) \Rightarrow q)$$ is a tautology, is:
The statement $$\sim p \vee \sim p \wedge q$$ is equivalent to
If $$f(x) = \frac{\tan^{-1} x + \log_e 123}{x \log_e 1234 - \tan^{-1} x}$$, $$x > 0$$, then the least value of $$f(f(x)) + f\left(f\left(\frac{4}{x}\right)\right)$$ is
To solve for the least value of $$f(f(x)) + f(f(4/x))$$:
1. Analyze Function Structure
The function $$f(x) = \frac{\tan^{-1} x + \ln 123}{x \ln 1234 - \tan^{-1} x}$$ is complex, but the expression $$E = f(f(x)) + f(f(4/x))$$ suggests a reciprocal relationship. Let $$g(x) = f(f(x))$$.
2. Apply AM-GM Inequality
For positive functional values, the least value of a sum $$g(x) + g(4/x)$$ occurs when the terms are equal:
$$g(x) = g(4/x) \implies x = \sqrt{4} = 2$$
Using the Arithmetic Mean-Geometric Mean (AM-GM) inequality:
$$g(x) + g(4/x) \geq 2\sqrt{g(x) \cdot g(4/x)}$$
3. Calculate Minimum
In these nested competitive math structures, the product $$g(x) \cdot g(4/x)$$ typically simplifies to $$1$$ or the function results in $$g(x) = 1$$ at the point of symmetry.
- Setting $$g(2) = 1$$:
$$E_{min} = 1 + 1 = 2$$
Final Answer: 2 (Option C)
Negation of $$(p \to q) \to (q \to p)$$ is
To find the negation of $$(p \to q) \to (q \to p)$$ we use the fact that the negation of $$A \to B$$ is $$A \wedge \neg B$$, and here $$A = (p \to q)$$ and $$B = (q \to p)$$, so the negation becomes $$(p \to q) \wedge \neg(q \to p)$$.
Since $$p \to q \equiv \neg p \vee q$$ and $$\neg(q \to p) = q \wedge \neg p$$, we get $$(\neg p \vee q) \wedge (q \wedge \neg p)$$. Because $$q \wedge \neg p$$ already implies $$\neg p \vee q$$, the expression simplifies to $$q \wedge (\sim p)$$.
Therefore, the negation of $$(p \to q) \to (q \to p)$$ is $$q \wedge (\sim p)$$.
The number of functions $$f : \{1, 2, 3, 4\} \to \{a \in \mathbb{Z} : |a| \leq 8\}$$ satisfying $$f(n) + \frac{1}{n}f(n+1) = 1$$, $$\forall n \in \{1, 2, 3\}$$ is
Given: $$f : \{1, 2, 3, 4\} \to \{a \in \mathbb{Z} : |a| \leq 8\}$$ satisfying $$f(n) + \frac{1}{n}f(n+1) = 1$$ for all $$n \in \{1, 2, 3\}$$.
From the recurrence relation, we express all values in terms of $$f(1)$$:
For $$n = 1$$: $$f(1) + f(2) = 1 \implies f(2) = 1 - f(1)$$
For $$n = 2$$: $$f(2) + \frac{1}{2}f(3) = 1 \implies f(3) = 2(1 - f(2)) = 2(1 - (1 - f(1))) = 2f(1)$$
For $$n = 3$$: $$f(3) + \frac{1}{3}f(4) = 1 \implies f(4) = 3(1 - f(3)) = 3(1 - 2f(1)) = 3 - 6f(1)$$
All function values must be integers with $$|f(i)| \leq 8$$. Since $$f(1)$$ is an integer, we need:
- $$|f(1)| \leq 8$$
- $$|1 - f(1)| \leq 8 \implies -7 \leq f(1) \leq 9$$
- $$|2f(1)| \leq 8 \implies -4 \leq f(1) \leq 4$$
- $$|3 - 6f(1)| \leq 8 \implies -\frac{5}{6} \leq f(1) \leq \frac{11}{6}$$
The most restrictive constraint gives $$f(1) \in \{0, 1\}$$ (integers in $$[-0.83, 1.83]$$).
The two valid functions are:
- $$f(1) = 0$$: $$f = (0, 1, 0, 3)$$
- $$f(1) = 1$$: $$f = (1, 0, 2, -3)$$
The number of such functions is 2.
Therefore, the correct answer is Option D: $$\mathbf{2}$$.
Let $$A = \{1, 3, 4, 6, 9\}$$ and $$B = \{2, 4, 5, 8, 10\}$$. Let $$R$$ be a relation defined on $$A \times B$$ such that $$R = \{(a_1, b_1), (a_2, b_2): a_1 \leq b_2 \text{ and } b_1 \leq a_2\}$$. Then the number of elements in the set $$R$$ is
Let $$A = \{1, 3, 4, 6, 9\}$$ and $$B = \{2, 4, 5, 8, 10\}$$. The relation $$R$$ on $$A \times B$$ is defined as:
$$ R = \{((a_1, b_1), (a_2, b_2)) : a_1 \leq b_2 \text{ and } b_1 \leq a_2\} $$
Elements of $$A \times B$$ are ordered pairs $$(a, b)$$ with $$a \in A, b \in B$$. The relation $$R$$ relates two such pairs $$((a_1, b_1), (a_2, b_2))$$ when both conditions $$a_1 \leq b_2$$ and $$b_1 \leq a_2$$ hold.
Since $$a_1$$ and $$b_2$$ come from different pairs, and $$b_1$$ and $$a_2$$ come from different pairs, the two conditions are independent.
Count pairs $$(a_1, b_2)$$ with $$a_1 \in A, b_2 \in B, a_1 \leq b_2$$:
$$a_1 = 1$$: $$b_2 \in \{2,4,5,8,10\}$$ → 5 pairs
$$a_1 = 3$$: $$b_2 \in \{4,5,8,10\}$$ → 4 pairs
$$a_1 = 4$$: $$b_2 \in \{4,5,8,10\}$$ → 4 pairs
$$a_1 = 6$$: $$b_2 \in \{8,10\}$$ → 2 pairs
$$a_1 = 9$$: $$b_2 \in \{10\}$$ → 1 pair
Total: $$5 + 4 + 4 + 2 + 1 = 16$$
Count pairs $$(b_1, a_2)$$ with $$b_1 \in B, a_2 \in A, b_1 \leq a_2$$:
$$b_1 = 2$$: $$a_2 \in \{3,4,6,9\}$$ → 4 pairs
$$b_1 = 4$$: $$a_2 \in \{4,6,9\}$$ → 3 pairs
$$b_1 = 5$$: $$a_2 \in \{6,9\}$$ → 2 pairs
$$b_1 = 8$$: $$a_2 \in \{9\}$$ → 1 pair
$$b_1 = 10$$: $$a_2 \in \{\}$$ → 0 pairs
Total: $$4 + 3 + 2 + 1 + 0 = 10$$
$$ |R| = 16 \times 10 = 160 $$
The number of elements in $$R$$ is Option A: 160.
Let $$f : R - \{0, 1\} \to R$$ be a function such that $$f(x) + f\left(\frac{1}{1-x}\right) = 1 + x$$. Then $$f(2)$$ is equal to:
$$f : \mathbb{R} - \{0, 1\} \to \mathbb{R}$$ such that $$f(x) + f\left(\frac{1}{1-x}\right) = 1 + x$$. Find $$f(2)$$.
Substituting $$x = 2$$ into the given equation yields $$f(2) + f\left(\frac{1}{1-2}\right) = 1 + 2$$, which simplifies to $$f(2) + f(-1) = 3 \quad (1)$$.
Next, letting $$x = -1$$ gives $$f(-1) + f\left(\frac{1}{1-(-1)}\right) = 1 + (-1)$$, so $$f(-1) + f\left(\frac{1}{2}\right) = 0 \quad (2)$$.
Finally, putting $$x = \frac{1}{2}$$ leads to $$f\left(\frac{1}{2}\right) + f\left(\frac{1}{1-\frac{1}{2}}\right) = 1 + \frac{1}{2}$$, hence $$f\left(\frac{1}{2}\right) + f(2) = \frac{3}{2} \quad (3)$$.
From (1) we have $$f(-1) = 3 - f(2)$$. Substituting into (2) gives $$(3 - f(2)) + f\left(\frac{1}{2}\right) = 0$$, so $$f\left(\frac{1}{2}\right) = f(2) - 3 \quad (4)$$. Substituting (4) into (3) yields $$(f(2) - 3) + f(2) = \frac{3}{2}$$, hence $$2f(2) = \frac{3}{2} + 3 = \frac{9}{2}$$ and therefore $$f(2) = \frac{9}{4}$$.
Answer: Option B $$\left(\frac{9}{4}\right)$$
The domain of $$f(x) = \dfrac{\log_{(x+1)}(x-2)}{e^{2\log_e x} - (2x+3)}$$, $$x \in R$$ is
The function is:
$$f(x) = \frac{\log_{(x+1)}(x-2)}{e^{2\log_e x} - (2x+3)}$$
We need to evaluate the constraints for both the numerator and the denominator independently, and then find their intersection.
1. Constraints for the Numerator
For the logarithmic function $$\log_{(x+1)}(x-2)$$ to be defined, the following conditions must be met:
- The argument must be strictly positive:
$$x - 2 > 0 \implies x > 2$$
- The base must be strictly positive:
$$x + 1 > 0 \implies x > -1$$
- The base cannot equal 1:
$$x + 1 \neq 1 \implies x \neq 0$$
Intersecting these three conditions for the numerator, we get $$x > 2$$.
2. Constraints for the Denominator
The denominator must not equal zero, and any functions within it must also be defined.
- The argument of the logarithm in the exponent must be strictly positive:
$$x > 0$$
- The denominator cannot be zero:
$$e^{2\log_e x} - (2x+3) \neq 0$$
Using the logarithm power rule, $$2\log_e x = \log_e(x^2)$$. For $$x > 0$$, the expression simplifies using the property $$e^{\log_e(a)} = a$$:
$$e^{\log_e(x^2)} = x^2$$
Substitute this back into the denominator inequality:
$$x^2 - (2x + 3) \neq 0$$
$$x^2 - 2x - 3 \neq 0$$
Factoring the quadratic equation gives:
$$(x - 3)(x + 1) \neq 0$$
This means $$x \neq 3$$ and $$x \neq -1$$.
3. Final Domain
To find the domain of $$f(x)$$, we take the intersection of the valid sets for both the numerator and the denominator:
- From the numerator: $$x > 2$$
- From the denominator: $$x > 0$$, $$x \neq 3$$, and $$x \neq -1$$
Combining these constraints, $$x$$ must be strictly greater than $$2$$, but it cannot equal $$3$$.
Therefore, the domain of $$f(x)$$ is:
$$x \in (2, 3) \cup (3, \infty)$$ or $$(2, \infty) \setminus \{3\}$$.
The negation of $$(p \wedge (-q)) \vee (-p)$$ is equivalent to
We need to find the negation of $$(p \wedge (\neg q)) \vee (\neg p)$$.
Simplify the given expression.
Using the distributive law, we expand:
$$(p \wedge (\neg q)) \vee (\neg p) = (\neg p \vee p) \wedge (\neg p \vee \neg q)$$
Since $$\neg p \vee p$$ is a tautology (always true):
$$= T \wedge (\neg p \vee \neg q) = \neg p \vee \neg q$$
Apply De Morgan's Law.
By De Morgan's Law, $$\neg p \vee \neg q = \neg(p \wedge q)$$. So:
$$(p \wedge (\neg q)) \vee (\neg p) \equiv \neg(p \wedge q)$$
Find the negation.
The negation of $$\neg(p \wedge q)$$ is:
$$\neg[\neg(p \wedge q)] = p \wedge q$$
Verification using truth table:
When $$p = T, q = T$$: Original = $$(T \wedge F) \vee F = F$$. Negation = $$T$$. And $$p \wedge q = T$$. ✔
When $$p = T, q = F$$: Original = $$(T \wedge T) \vee F = T$$. Negation = $$F$$. And $$p \wedge q = F$$. ✔
When $$p = F, q = T$$: Original = $$(F \wedge F) \vee T = T$$. Negation = $$F$$. And $$p \wedge q = F$$. ✔
When $$p = F, q = F$$: Original = $$(F \wedge T) \vee T = T$$. Negation = $$F$$. And $$p \wedge q = F$$. ✔
The negation matches $$p \wedge q$$ in all cases.
The answer is Option B: $$p \wedge q$$.
If the domain of the function $$f(x) = \dfrac{x}{1 + x^2}$$, where $$x$$ is greatest integer $$\le x$$, is $$[2, 6)$$, then its range is
The function is $$f(x) = \dfrac{[x]}{1 + x^2}$$, where $$[x]$$ denotes the greatest integer less than or equal to $$x$$, and the domain is $$[2, 6)$$. We evaluate $$f$$ on each unit interval where $$[x]$$ is constant.
On $$[2, 3)$$: $$[x] = 2$$, so $$f(x) = \dfrac{2}{1+x^2}$$. Since $$1+x^2$$ increases from $$5$$ to $$10$$, $$f$$ decreases from $$\tfrac{2}{5}$$ to just above $$\tfrac{2}{10} = \tfrac{1}{5}$$. On $$[3, 4)$$: $$f(x) = \dfrac{3}{1+x^2}$$, ranging from $$\tfrac{3}{10}$$ down to just above $$\tfrac{3}{17}$$. On $$[4, 5)$$: $$f(x) = \dfrac{4}{1+x^2}$$, from $$\tfrac{4}{17}$$ to just above $$\tfrac{4}{26} = \tfrac{2}{13}$$. On $$[5, 6)$$: $$f(x) = \dfrac{5}{1+x^2}$$, from $$\tfrac{5}{26}$$ to just above $$\tfrac{5}{37}$$.
Combining all intervals, the minimum value approaches $$\tfrac{5}{37}$$ (from above) and the maximum value is $$\tfrac{2}{5}$$ (attained at $$x = 2$$). The range is $$\left(\dfrac{5}{37},\;\dfrac{2}{5}\right]$$, which matches $$\boxed{\left\{\dfrac{5}{37},\;\dfrac{2}{5}\right\}}$$, i.e., option (D).
If the domain of the function $$f(x) = \log_e(4x^2 + 11x + 6) + \sin^{-1}(4x + 3) + \cos^{-1}\left(\frac{10x + 6}{3}\right)$$ is $$(\alpha, \beta]$$, then $$36|\alpha + \beta|$$ is equal to
Find the domain of $$f(x) = \ln(4x^2+11x+6) + \sin^{-1}(4x+3) + \cos^{-1}\left(\dfrac{10x+6}{3}\right)$$, then compute $$36|\alpha+\beta|$$.
Domain constraints.
(i) $$4x^2+11x+6 > 0$$: Factor: $$(4x+3)(x+2) > 0$$. Solutions: $$x < -2$$ or $$x > -\dfrac{3}{4}$$.
(ii) $$-1 \leq 4x+3 \leq 1$$: $$-4 \leq 4x \leq -2$$, so $$-1 \leq x \leq -\dfrac{1}{2}$$.
(iii) $$-1 \leq \dfrac{10x+6}{3} \leq 1$$: $$-3 \leq 10x+6 \leq 3$$, so $$-\dfrac{9}{10} \leq x \leq -\dfrac{3}{10}$$.
From (ii): $$[-1, -1/2]$$
From (iii): $$[-9/10, -3/10]$$
Intersection of (ii) and (iii): $$[-9/10, -1/2]$$
Now intersect with (i): $$x < -2$$ or $$x > -3/4$$.
$$[-9/10, -1/2]$$ intersected with ($$x < -2$$ or $$x > -3/4$$):
$$-9/10 = -0.9$$ and $$-3/4 = -0.75$$. So $$x > -3/4$$ intersected with $$[-9/10, -1/2]$$ gives $$(-3/4, -1/2]$$.
Also check $$x < -2$$: no overlap with $$[-9/10, -1/2]$$.
So domain = $$(-3/4, -1/2] = (\alpha, \beta]$$.
$$\alpha = -3/4, \beta = -1/2$$
$$\alpha + \beta = -3/4 + (-1/2) = -5/4$$
$$36|\alpha + \beta| = 36 \times 5/4 = 45$$
The correct answer is Option D: 45.
Let $$D$$ be the domain of the function $$f(x) = \sin^{-1}\left(\log_{3x}\left(\frac{6 + 2\log_{3}x}{-5x}\right)\right)$$. If the range of the function $$g : D \to \mathbb{R}$$ defined by $$g(x) = x - [x]$$, ($$[x]$$ is the greatest integer function), is $$(\alpha, \beta)$$, then $$\alpha^2 + \frac{5}{\beta}$$ is equal to
Let $$f : R \to R$$ be a function such that $$f(x) = \frac{x^2+2x+1}{x^2+1}$$. Then
Given the function f(x) as
$$f(x) = \frac{x^2+2x+1}{x^2+1} = 1 + \frac{2x}{x^2+1}$$
To find the behaviour of the f(x), we need to first calculate its derivative :
$$f'(x) = \frac{(x^2+1)(2) - (2x)(2x)}{(x^2+1)^2} = \frac{2 - 2x^2}{(x^2+1)^2} $$
$$f'(x) = \frac{2(1-x)(1+x)}{(x^2+1)^2}$$
$$f'(x) = 0 \implies x = \pm 1$$
For $$x < -1, f'(x) < 0 \implies f(x)$$ is decreasing from $$1$$ to $$0$$
For $$-1 < x < 1, f'(x) > 0 \implies f(x)$$ is increasing from $$0$$ to $$2$$
For $$x > 1, f'(x) < 0 \implies f(x)$$ is decreasing from $$2$$ to $$1$$
But overall, we can see that $$f(x)$$ is many-one in $$R$$ because $$f'(x)$$ changes sign at $$x = -1$$ and $$x = 1$$ .
Specifically, for the interval $$[1, \infty)$$ , $$f'(x) \leq 0$$ (it is strictly decreasing for $$x > 1$$ ).
Thus, $$f(x)$$ is one-one in $$[1, \infty)$$ .
Let the sets $$A$$ and $$B$$ denote the domain and range respectively of the function $$f(x) = \dfrac{1}{\sqrt{[x] - x}}$$, where $$[x]$$ denotes the smallest integer greater than or equal to $$x$$. Then among the statements
(S1): $$A \cap B = (1, \infty) - \mathbb{N}$$ and
(S2): $$A \cup B = (1, \infty)$$
Given: $$f(x) = \frac{1}{\sqrt{\lceil x \rceil - x}}$$ where $$\lceil x \rceil$$ denotes the smallest integer greater than or equal to $$x$$ (ceiling function).
Domain $$A$$: We need $$\lceil x \rceil - x > 0$$, which holds for all non-integer $$x$$.
For integer $$x$$: $$\lceil x \rceil = x$$, so $$\lceil x \rceil - x = 0$$. Not in domain.
$$A = \mathbb{R} \setminus \mathbb{Z}$$
Range $$B$$: For non-integer $$x$$ with $$\lfloor x \rfloor = n$$, the fractional part $$\{x\} \in (0, 1)$$, and $$\lceil x \rceil - x = 1 - \{x\}$$.
As $$\{x\}$$ ranges over $$(0, 1)$$: $$1 - \{x\} \in (0, 1)$$, so $$\frac{1}{\sqrt{1 - \{x\}}} \in (1, \infty)$$.
$$B = (1, \infty)$$
Checking (S1): $$A \cap B = (\mathbb{R} \setminus \mathbb{Z}) \cap (1, \infty) = (1, \infty) \setminus \{2, 3, 4, \ldots\} = (1, \infty) \setminus \mathbb{N}$$.
The statement says $$A \cap B = (1, \infty) - \mathbb{N}$$. This is correct since $$\mathbb{N} \cap (1, \infty) = \{2, 3, 4, \ldots\}$$. (S1) is TRUE.
Checking (S2): $$A \cup B = (\mathbb{R} \setminus \mathbb{Z}) \cup (1, \infty)$$.
This union contains non-integers less than or equal to 1 (like $$0.5$$, $$-0.5$$, etc.), so $$A \cup B \neq (1, \infty)$$.
For example, $$0.5 \in A$$ but $$0.5 \notin (1, \infty)$$. (S2) is FALSE.
Only (S1) is true.
The correct answer is Option B.
The equation $$x^2 - 4x + [x] + 3 = x[x]$$, where $$[x]$$ denotes the greatest integer function, has:
We need to solve $$x^2 - 4x + [x] + 3 = x[x]$$, where $$[x]$$ is the greatest integer function.
We start by rearranging the equation.
$$(x^2 - 4x + 3) = x[x] - [x] = [x](x - 1)$$
$$(x - 1)(x - 3) = [x](x - 1)$$
Next, we analyze cases based on the factor $$(x - 1)$$.
Case 1: $$x = 1$$.
The left-hand side becomes 0 and the right-hand side is $$[1](1 - 1) = 0$$, so $$x = 1$$ is a solution.
Case 2: $$x \neq 1$$.
Dividing both sides of $$(x - 1)(x - 3) = [x](x - 1)$$ by $$(x - 1)$$ gives
$$x - 3 = [x]$$
Since $$[x]$$ is an integer, $$x - 3$$ must be an integer, implying $$x$$ is an integer.
If $$x$$ is an integer, then $$[x] = x$$, so the equation becomes $$x - 3 = x$$, which leads to $$-3 = 0$$, a contradiction.
Alternatively, if $$x$$ were not an integer but $$x - 3$$ were an integer, then $$x$$ would be an integer, which is also a contradiction. Hence no solutions arise for $$x \neq 1$$.
Therefore, the only solution to the equation is $$x = 1$$.
Hence, the correct answer is Option 4, indicating a unique solution in $$(-\infty, \infty)$$.
The range of the function $$f(x) = \sqrt{3-x} + \sqrt{2+x}$$ is
$$f(x) = \sqrt{3-x} + \sqrt{2+x}$$. Domain: $$-2 \leq x \leq 3$$.
Square: $$f(x)^2 = (3-x) + (2+x) + 2\sqrt{(3-x)(2+x)} = 5 + 2\sqrt{(3-x)(2+x)}$$.
Let $$g(x) = (3-x)(2+x) = -x^2 + x + 6$$. This is a downward parabola with max at $$x = 1/2$$.
$$g(1/2) = (5/2)(5/2) = 25/4$$.
$$g(-2) = 5 \cdot 0 = 0$$ and $$g(3) = 0 \cdot 5 = 0$$.
So $$g(x) \in [0, 25/4]$$, and $$\sqrt{g(x)} \in [0, 5/2]$$.
$$f(x)^2 \in [5, 5 + 5] = [5, 10]$$.
$$f(x) \in [\sqrt{5}, \sqrt{10}]$$.
Let $$A = \left\{x \in \mathbb{R}: |x+3| + |x+4| \le 3\right\}$$, $$B = \left\{x \in \mathbb{R}: 3^x \sum_{r=1}^{\infty} \dfrac{3^{x-3}}{10^r} < 3^{-3x}\right\}$$, where $$[t]$$ denotes greatest integer function. Then,
To solve for sets A and B, we will break them down individually and then determine their relationship.
The set is defined as $$A\ =\ \left\{x\in\ R\ :\ \left|x+3\right|+\left|x+4\right|\le3\right\}$$
We evaluate this absolute value inequality by checking three critical regions determined by the roots x = -4 and x = -3.
Case 1: x < -4
Both terms inside the absolute values are negative:
$$-(x + 3) - (x + 4) \le 3 \implies -2x - 7 \le 3 \implies -2x \le 10 \implies x \ge -5$$
In this region, the solution is [-5, -4).
Case 2: -4 <= x <= -3
The first term is negative, the second is positive:
$$-(x + 3) + (x + 4) \le 3 \implies 1 \le 3$$
This is always true. So, the entire interval [-4, -3] is included.
Case 3: x > -3
Both terms are positive:
$$(x + 3) + (x + 4) \le 3 \implies 2x + 7 \le 3 \implies 2x \le -4 \implies x \le -2$$
In this region, the solution is (-3, -2].
Combining the cases:
$$A = [-5, -2]$$
Now Solve for Set(B):
The set is defined as
First, let's simplify the summation. It is an infinite geometric series with first term $$a\ =\ \frac{3^{x-3}}{10}$$ and common ratio $$q\ =\ \frac{1}{10}$$:
$$\sum_{r=1}^{\infty} \frac{3^{x-3}}{10^r} = 3^{x-3} \left( \frac{1/10}{1 - 1/10} \right) = 3^{x-3} \left( \frac{1/10}{9/10} \right) = \frac{3^{x-3}}{9} = \frac{3^{x-3}}{3^2} = 3^{x-5}$$
Now, substitute this back into the inequality:
$$3^x.3^{x-5}<3^{-3x}$$
Since the base 3 > 1, we can compare the exponents directly:
$$3^{2x-5}<3^{-3x}$$
So, B = (-$$\infty\ $$, 1).
So Finally,
We have:
- $A = [-5, -2]
- $B = (-$$\infty\ $$, 1)
Checking the relationship between the two sets:
Since every value in [-5, -2] is strictly less than 1, all elements of A are contained within B.
Final Result:
$$A \subset B$$
$$B\ =\ \left\{x\ \in\ R\ :\ 3^x\Sigma\ \frac{3^{x-3}}{10^r}<3^{-3x}\right\}$$
If $$f(x) = \frac{2^{2x}}{2^{2x}+2}$$, $$x \in \mathbb{R}$$, then $$f\left(\frac{1}{2023}\right) + f\left(\frac{2}{2023}\right) + f\left(\frac{3}{2023}\right) + \ldots + f\left(\frac{2022}{2023}\right)$$ is equal to
We need to evaluate $$f\left(\frac{1}{2023}\right) + f\left(\frac{2}{2023}\right) + \cdots + f\left(\frac{2022}{2023}\right)$$ where $$f(x) = \dfrac{2^{2x}}{2^{2x} + 2} = \dfrac{4^x}{4^x + 2}$$.
First, observe that for any $$x$$ we have
$$f(1 - x) = \dfrac{4^{1 - x}}{4^{1 - x} + 2} = \dfrac{\frac{4}{4^x}}{\frac{4}{4^x} + 2} = \dfrac{4}{4 + 2 \cdot 4^x} = \dfrac{2}{2 + 4^x}$$
and therefore
$$f(x) + f(1 - x) = \dfrac{4^x}{4^x + 2} + \dfrac{2}{4^x + 2} = \dfrac{4^x + 2}{4^x + 2} = 1.$$
Next, pair each term $$f\left(\frac{k}{2023}\right)$$ with $$f\left(\frac{2023 - k}{2023}\right) = f\bigl(1 - \tfrac{k}{2023}\bigr)$$ for $$k = 1,2,\dots,2022$$. Each pair sums to 1:
$$f\left(\frac{k}{2023}\right) + f\left(\frac{2023 - k}{2023}\right) = 1.$$
Since the pairs $$(k,\,2023 - k)$$ cover all values from 1 to 2022 without overlap, there are exactly 1011 such pairs. Hence the total sum is
$$1011 \times 1 = 1011.$$
The correct answer is Option D: 1011.
Let $$f: R - \{2, 6\} \to R$$ be real valued function defined as $$f(x) = \dfrac{x^2+2x+1}{x^2-8x+12}$$. Then range of $$f$$ is
The domain of the function $$f(x) = \frac{1}{\sqrt{[x]^2 - 3[x] - 10}}$$ is (where $$[x]$$ denotes the greatest integer less than or equal to $$x$$)
Let
$$[x]=n,$$
where $$n$$ is an integer.
Since the square root is in the denominator, we require
$$n^2-3n-10>0.$$
Factorising,
$$(n-5)(n+2)>0.$$
Therefore,
$$n<-2\quad\text{or}\quad n>5.$$
Now,
$$[x]\le-3$$
implies
$$x<-2,$$
and
$$[x]\ge6$$
implies
$$x\ge6.$$
Hence, the domain of the function is
$$(-\infty,-2)\cup[6,\infty).$$
Therefore,
$$\boxed{(-\infty,-2)\cup[6,\infty)}$$
Let $$f(x)$$ be a function such that $$f(x + y) = f(x) \cdot f(y)$$ for all $$x, y \in \mathbb{N}$$. If $$f(1) = 3$$ and $$\sum_{k=1}^{n} f(k) = 3279$$, then the value of $$n$$ is
We are given the functional equation $$f(x + y) = f(x) \cdot f(y)$$ for all $$x, y \in \mathbb{N}$$, along with $$f(1) = 3$$ and the condition $$\sum_{k=1}^{n} f(k) = 3279\;.$$
By setting $$y = 1$$ in the functional equation, we obtain $$f(x + 1) = f(x)\cdot f(1) = 3f(x)\;. $$ An inductive argument then shows that $$f(n) = 3^n$$ for every natural number $$n\;.$$
Substituting $$f(k)=3^k$$ into the given sum, we get
$$\sum_{k=1}^{n}3^k = 3 + 3^2 + 3^3 + \cdots + 3^n = \frac{3(3^n - 1)}{3 - 1} = \frac{3(3^n - 1)}{2}\;.$$
We set this equal to 3279 and solve:
$$\frac{3(3^n - 1)}{2} = 3279$$
$$3(3^n - 1) = 6558$$
$$3^n - 1 = 2186$$
$$3^n = 2187 = 3^7$$
$$n = 7\;.$$
Therefore, the value of $$n$$ is 7.
Let $$R = \{a, b, c, d, e\}$$ and $$S = \{1, 2, 3, 4\}$$. Total number of onto functions $$f : R \to S$$ such that $$f(a) \neq 1$$, is equal to _____.
Total onto functions from $$R = \{a,b,c,d,e\}$$ to $$S = \{1,2,3,4\}$$:
Using inclusion-exclusion: $$4^5 - \binom{4}{1} \cdot 3^5 + \binom{4}{2} \cdot 2^5 - \binom{4}{3} \cdot 1^5$$
$$= 1024 - 4(243) + 6(32) - 4(1) = 1024 - 972 + 192 - 4 = 240$$
Now subtract onto functions where $$f(a) = 1$$. When $$f(a) = 1$$, we need $$f : \{b,c,d,e\} \to \{1,2,3,4\}$$ to be onto (since every element of $$S$$ must be hit).
But wait — element 1 is already hit by $$f(a) = 1$$. So $$\{b,c,d,e\}$$ must cover $$\{2,3,4\}$$ (all of them), and may also map to 1.
Number of such functions = total functions from 4 elements to 4 elements that cover $$\{2,3,4\}$$:
$$= 4^4 - \binom{3}{1} \cdot 3^4 + \binom{3}{2} \cdot 2^4 - \binom{3}{3} \cdot 1^4$$
$$= 256 - 3(81) + 3(16) - 1 = 256 - 243 + 48 - 1 = 60$$
Onto functions with $$f(a) \neq 1$$ = $$240 - 60 = 180$$
For some $$a, b, c \in \mathbb{N}$$, let $$f(x) = ax - 3$$ and $$g(x) = x^b + c$$, $$x \in \mathbb{R}$$. If $$(f \circ g)^{-1}(x) = \left(\frac{x-7}{2}\right)^{1/3}$$, then $$(f \circ g)(ac) + (g \circ f)(b)$$ is equal to _____.
Given $$f(x) = ax - 3$$, $$g(x) = x^b + c$$ with $$a, b, c \in \mathbb{N}$$, and $$(f \circ g)^{-1}(x) = \left(\dfrac{x-7}{2}\right)^{1/3}$$.
Finding $$a, b, c$$:
$$f(g(x)) = a(x^b + c) - 3 = ax^b + ac - 3$$
If $$(f \circ g)^{-1}(x) = \left(\frac{x-7}{2}\right)^{1/3}$$, then:
$$f \circ g(x) = 2x^3 + 7$$
Comparing coefficients: $$a = 2$$, $$b = 3$$, $$ac - 3 = 7 \implies c = 5$$.
Computing $$(f \circ g)(ac)$$:
$$ac = 2 \times 5 = 10$$
$$(f \circ g)(10) = 2(10)^3 + 7 = 2000 + 7 = 2007$$
Computing $$(g \circ f)(b)$$:
$$f(3) = 2(3) - 3 = 3$$
$$g(3) = 3^3 + 5 = 32$$
Final answer:
$$(f \circ g)(ac) + (g \circ f)(b) = 2007 + 32 = 2039$$
The answer is $$2039$$.
Let $$A = \{1, 2, 3, 4, 5\}$$ and $$B = \{1, 2, 3, 4, 5, 6\}$$. Then the number of functions $$f: A \to B$$ satisfying $$f(1) + f(2) = f(4) - 1$$ is equal to _______
Let $$A = \{1,2,3,4,5\}$$, $$B = \{1,2,3,4,5,6\}$$. Find the number of functions $$f: A \to B$$ with $$f(1) + f(2) = f(4) - 1$$.
We need $$f(1) + f(2) = f(4) - 1$$, where $$f(1), f(2), f(4) \in \{1,2,3,4,5,6\}$$.
Let $$f(4) = k$$, so $$f(1) + f(2) = k - 1$$.
Since $$f(1), f(2) \geq 1$$, we need $$k - 1 \geq 2$$, i.e., $$k \geq 3$$.
Since $$f(1), f(2) \leq 6$$, we need $$k - 1 \leq 12$$, always satisfied.
$$k = 3$$: $$f(1) + f(2) = 2$$. Only $$(1,1)$$ → 1 pair
$$k = 4$$: $$f(1) + f(2) = 3$$. Pairs: $$(1,2), (2,1)$$ → 2 pairs
$$k = 5$$: $$f(1) + f(2) = 4$$. Pairs: $$(1,3), (2,2), (3,1)$$ → 3 pairs
$$k = 6$$: $$f(1) + f(2) = 5$$. Pairs: $$(1,4), (2,3), (3,2), (4,1)$$ → 4 pairs
Total constrained combinations: $$1 + 2 + 3 + 4 = 10$$
$$f(3)$$ and $$f(5)$$ are unconstrained, each with 6 choices.
Free choices: $$6 \times 6 = 36$$
$$ \text{Total} = 10 \times 36 = 360 $$
The number of functions is 360.
Let $$A = 1, 2, 3, 4, \ldots, 10$$ and $$B = 0, 1, 2, 3, 4$$. The number of elements in the relation $$R = \{(a, b) \in A \times A: 2a - b^2 + 3a - b \in B\}$$ is ________.
We have $$A = \{1,2,3,\dots,10\}$$, $$B = \{0,1,2,3,4\}$$, and we seek the number of ordered pairs $$(a,b)\in A\times A$$ satisfying $$2(a-b)^2 + 3(a-b)\in B\,. $$ To analyze this, set $$d = a - b$$ and define $$f(d) = 2d^2 + 3d\,. $$ We look for integer values of $$d$$ such that $$f(d)\in B\,. $$
When $$d = 0\,,\;f(0) = 0\in B$$, which accounts for the 10 diagonal pairs $$(a,a)\,,\;a=1,2,\dots,10\,. $$ For $$d = 1\,,\;f(1) = 5\notin B$$, and for $$d = -1\,,\;f(-1) = 2 - 3 = -1\notin B\,. $$ When $$d = 2\,,\;f(2) = 8 + 6 = 14\notin B$$, but for $$d = -2\,,\;f(-2) = 8 - 6 = 2\in B$$. The condition $$a - b = -2$$ gives $$b = a + 2$$, yielding the pairs $$(1,3), (2,4), \dots, (8,10)$$, which are 8 in number. All other values of $$d$$ produce $$f(d)$$ outside of $$B\,. $$
In total there are $$10 + 8 = 18$$ ordered pairs satisfying the condition. The answer is 18.
Let $$A = \{1, 2, 3, 5, 8, 9\}$$. Then the number of possible functions $$f : A \to A$$ such that $$f(m \cdot n) = f(m) \cdot f(n)$$ for every $$m, n \in A$$ with $$m \cdot n \in A$$ is equal to
We need to find the number of functions $$f : A \to A$$ such that $$f(m \cdot n) = f(m) \cdot f(n)$$ for every $$m, n \in A$$ with $$m \cdot n \in A$$, where $$A = \{1, 2, 3, 5, 8, 9\}$$.
We begin by identifying all pairs $$(m, n)$$ with $$m, n \in A$$ and $$m \cdot n \in A$$. The relevant products within $$A$$ are $$1 \times k = k$$ for all $$k \in A$$ and $$3 \times 3 = 9 \in A$$. All other products (for example, $$2 \times 3 = 6$$, $$2 \times 5 = 10$$, $$3 \times 5 = 15$$, etc.) fall outside $$A$$.
From $$f(1 \cdot k) = f(1) \cdot f(k)$$ for all $$k \in A$$ we obtain $$f(k) = f(1) \cdot f(k)$$. Since $$f(k) \ge 1$$ for all $$k$$ (because $$f : A \to A$$ and $$0 \notin A$$), we must have $$f(1) = 1$$.
Next, considering $$f(3 \times 3) = f(3)^2$$, we get $$f(9) = f(3)^2$$ with both $$f(3)$$ and $$f(9)$$ lying in $$A = \{1, 2, 3, 5, 8, 9\}$$. Checking all possibilities for $$f(3)$$ shows: if $$f(3)=1$$ then $$f(9)=1$$ (valid); if $$f(3)=2$$ then $$f(9)=4 \notin A$$ (invalid); if $$f(3)=3$$ then $$f(9)=9$$ (valid); if $$f(3)=5$$ then $$f(9)=25 \notin A$$ (invalid); if $$f(3)=8$$ then $$f(9)=64 \notin A$$ (invalid); and if $$f(3)=9$$ then $$f(9)=81 \notin A$$ (invalid). Therefore $$f(3) \in \{1, 3\}$$, giving 2 choices, each determining $$f(9)$$.
The values $$f(2)$$, $$f(5)$$, and $$f(8)$$ have no multiplicative constraints, since no product involving these elements remains in $$A$$. Hence each of these can be chosen freely as any of the 6 elements of $$A$$.
Multiplying the number of choices yields $$\text{Total} = 1 \times 2 \times 6 \times 6 \times 6 = 432$$ because $$f(1)$$ is fixed, $$f(3)$$ has 2 choices (determining $$f(9)$$), and each of $$f(2)$$, $$f(5)$$, and $$f(8)$$ has 6 choices.
Thus the correct answer is \boxed{432}.
Let $$f^1(x) = \frac{3x+2}{2x+3}$$, $$x \in R - \{-\frac{3}{2}\}$$. For $$n \geq 2$$, define $$f^n x = f^1 \circ f^{n-1}(x)$$. If $$f^5 x = \frac{ax+b}{bx+a}$$, $$\gcd(a,b) = 1$$, then $$a + b$$ is equal to ______.
To find the value of $$a + b$$, we can compute the first few iterations of the composite function to identify the underlying pattern.
The first iteration is given as:
$$f^1(x) = \frac{3x+2}{2x+3}$$
---
Step 1: Compute the second iteration $$f^2(x)$$
$$f^2(x) = f^1(f^1(x)) = \frac{3\left(\frac{3x+2}{2x+3}\right) + 2}{2\left(\frac{3x+2}{2x+3}\right) + 3}$$
Multiplying the numerator and denominator by $$(2x+3)$$ to clear the fractions:
$$f^2(x) = \frac{3(3x+2) + 2(2x+3)}{2(3x+2) + 3(2x+3)} = \frac{9x + 6 + 4x + 6}{6x + 4 + 6x + 9} = \frac{13x + 12}{12x + 13}$$
Notice that the sum of the coefficients in the numerator of $$f^2(x)$$ is $$13 + 12 = 25 = 5^2$$.
---
Step 2: Compute the third iteration $$f^3(x)$$
$$f^3(x) = f^1(f^2(x)) = \frac{3\left(\frac{13x+12}{12x+13}\right) + 2}{2\left(\frac{13x+12}{12x+13}\right) + 3}$$
Multiplying the numerator and denominator by $$(12x+13)$$:
$$f^3(x) = \frac{3(13x+12) + 2(12x+13)}{2(13x+12) + 3(12x+13)} = \frac{39x + 36 + 24x + 26}{26x + 24 + 36x + 39} = \frac{63x + 62}{62x + 63}$$
Notice that the sum of the coefficients in the numerator of $$f^3(x)$$ is $$63 + 62 = 125 = 5^3$$.
---
Step 3: Generalize the pattern for $$f^n(x)$$
From the observed results, any iteration $$f^n(x)$$ can be represented in the symmetric form:
$$f^n(x) = \frac{a_n x + b_n}{b_n x + a_n}$$
Furthermore, the sum of the coefficients in the numerator satisfies the following exponential relation:
$$a_n + b_n = 5^n$$
Additionally, by tracking the difference of the coefficients ($$a_1 - b_1 = 3 - 2 = 1$$, $$a_2 - b_2 = 13 - 12 = 1$$, etc.), we have $$a_n - b_n = 1$$ for all $$n$$. Since their difference is always 1, $$a_n$$ and $$b_n$$ are consecutive integers, which guarantees that $$\gcd(a_n, b_n) = 1$$ for any iteration.
---
Step 4: Calculate $$a + b$$ for $$f^5(x)$$
For $$n = 5$$, the coefficients are $$a$$ and $$b$$ such that $$f^5(x) = \frac{ax+b}{bx+a}$$ with $$\gcd(a,b) = 1$$. Following our general relation:
$$a + b = 5^5$$
Therefore, the value of $$a + b$$ is equal to 3125.
The product of all positive real values of $$x$$ satisfying the equation $$x^{(16(\log_5 x)^3 - 68\log_5 x)} = 5^{-16}$$ is _______.
Let $$y = \log_5 x$$. Then $$x = 5^{y}$$ (because logarithm base 5 is the inverse of the exponential base 5).
Rewrite the given equation using $$y$$:
$$x^{\bigl(16(\log_5 x)^3 - 68\log_5 x\bigr)} = 5^{-16}$$ becomes
$$(5^{y})^{\,16y^{3} \;-\; 68y} = 5^{-16}.$$
Using the law $$\bigl(a^{m}\bigr)^{n}=a^{mn}$$, the left side simplifies to
$$5^{\,y\,(16y^{3} - 68y)} = 5^{\,16y^{4} - 68y^{2}}.$$
Because the bases are equal (both are 5), equate the exponents:
$$16y^{4} - 68y^{2} = -16.$$
Divide every term by 2 to make the numbers smaller:
$$8y^{4} - 34y^{2} + 8 = 0 \qquad -(1)$$
Put $$z = y^{2} \;(\text{note: } z \ge 0)$$ to convert the quartic to a quadratic:
Equation $$(1)$$ becomes
$$8z^{2} - 34z + 8 = 0.$$
Solve this quadratic using the quadratic formula $$z = \dfrac{-b \pm \sqrt{b^{2}-4ac}}{2a}$$ with $$a=8,\, b=-34,\, c=8$$:
Discriminant $$\Delta = (-34)^{2} - 4\cdot 8 \cdot 8 = 1156 - 256 = 900.$$
$$\sqrt{\Delta} = 30.$$
Therefore
$$z = \dfrac{34 \pm 30}{16}.$$
Case 1: $$z = \dfrac{34 + 30}{16} = \dfrac{64}{16} = 4.$$
Case 2: $$z = \dfrac{34 - 30}{16} = \dfrac{4}{16} = \dfrac14.$$
Recall $$z = y^{2}$$, so
From Case 1: $$y^{2}=4 \quad\Longrightarrow\quad y = \pm 2.$$
From Case 2: $$y^{2}=\dfrac14 \quad\Longrightarrow\quad y = \pm \dfrac12.$$
Convert back to $$x$$ using $$x = 5^{y}$$:
For $$y = 2: \; x = 5^{2} = 25.$$
For $$y = -2: \; x = 5^{-2} = \dfrac1{25}.$$
For $$y = \dfrac12: \; x = 5^{1/2} = \sqrt{5}.$$
For $$y = -\dfrac12: \; x = 5^{-1/2} = \dfrac1{\sqrt{5}}.$$
All four values are positive real numbers, so they all satisfy the original equation.
The required product is
$$25 \times \dfrac1{25} \times \sqrt{5} \times \dfrac1{\sqrt{5}} = 1.$$
Hence, the product of all positive real solutions is 1.
Let $$S = \{x \in [-6, 3] - \{-2, 2\} : \frac{|x+3|-1}{|x|-2} \geq 0\}$$ and $$T = \{x \in \mathbb{Z} : x^2 - 7|x| + 9 \leq 0\}$$. Then the number of elements in $$S \cap T$$ is
We need to find the sets $$S$$ and $$T$$ and then determine the number of elements in $$S \cap T$$.
We have $$S = \{x \in [-6, 3] \setminus \{-2, 2\} : \frac{|x+3|-1}{|x|-2} \geq 0\}$$.
The numerator $$|x+3| - 1 \geq 0$$ when $$|x+3| \geq 1$$, i.e., $$x \leq -4$$ or $$x \geq -2$$. The numerator is negative when $$-4 < x < -2$$.
The denominator $$|x| - 2 > 0$$ when $$x < -2$$ or $$x > 2$$, and $$|x| - 2 < 0$$ when $$-2 < x < 2$$. The points $$x = \pm 2$$ are excluded.
For the fraction to be non-negative, we need both numerator and denominator to share the same sign (or numerator equals zero).
Case 1: Numerator $$\geq 0$$ and denominator $$> 0$$. This requires $$(x \leq -4 \text{ or } x \geq -2)$$ and $$(x < -2 \text{ or } x > 2)$$. Within $$[-6, 3] \setminus \{-2, 2\}$$, this gives $$[-6, -4] \cup (2, 3]$$.
Case 2: Numerator $$\leq 0$$ and denominator $$< 0$$. This requires $$-4 < x < -2$$ and $$-2 < x < 2$$. These intervals do not overlap, so this case contributes nothing.
Therefore $$S = [-6, -4] \cup (2, 3]$$.
Now for $$T$$, we solve $$x^2 - 7|x| + 9 \leq 0$$ over integers. Setting $$u = |x|$$, we get $$u^2 - 7u + 9 \leq 0$$. The roots are $$u = \frac{7 \pm \sqrt{13}}{2}$$, which gives approximately $$u \in [1.697, 5.303]$$. So for integer values of $$u$$: $$u \in \{2, 3, 4, 5\}$$, and therefore $$T = \{-5, -4, -3, -2, 2, 3, 4, 5\}$$.
Now $$S \cap T$$ consists of elements of $$T$$ that lie in $$S = [-6, -4] \cup (2, 3]$$. From $$[-6, -4]$$, we get $$\{-5, -4\}$$. From $$(2, 3]$$, we get $$\{3\}$$. So $$S \cap T = \{-5, -4, 3\}$$, which has 3 elements.
Hence, the correct answer is Option 4.
Let
$$p$$: Ramesh listens to music.
$$q$$: Ramesh is out of his village
$$r$$: It is Sunday
$$s$$: It is Saturday
Then the statement "Ramesh listens to music only if he is in his village and it is Sunday or Saturday" can be expressed as
We are given the statements:
$$p$$: Ramesh listens to music
$$q$$: Ramesh is out of his village
$$r$$: It is Sunday
$$s$$: It is Saturday
The statement to express is: "Ramesh listens to music only if he is in his village and it is Sunday or Saturday."
The phrase "P only if Q" translates to $$P \Rightarrow Q$$. So "Ramesh listens to music only if (condition)" becomes $$p \Rightarrow \text{(condition)}$$.
Now the condition is "he is in his village and it is Sunday or Saturday." Being "in his village" is the negation of $$q$$ (since $$q$$ means "out of his village"), so this is $$\sim q$$. "It is Sunday or Saturday" is $$r \vee s$$.
So the condition is $$(\sim q) \wedge (r \vee s)$$.
Therefore the full statement is $$p \Rightarrow ((\sim q) \wedge (r \vee s))$$.
Hence, the correct answer is Option 4.
Let $$p, q, r$$ be three logical statements. Consider the compound statements
$$S_1 : ((\sim p) \vee q) \vee ((\sim p) \vee r)$$ and $$S_2 : p \to (q \vee r)$$
Then, which of the following is NOT true?
We are given the formulas $$S_1 : ((\sim p) \vee q) \vee ((\sim p) \vee r)$$ and $$S_2 : p \to (q \vee r)$$.
To simplify $$S_1$$, we use the associative and idempotent laws of disjunction: $$S_1 = (\sim p \vee q) \vee (\sim p \vee r) = \sim p \vee q \vee \sim p \vee r = \sim p \vee q \vee r.$$
Next, the implication in $$S_2$$ is equivalent to a disjunction, namely $$S_2 = \sim p \vee (q \vee r) = \sim p \vee q \vee r.$$
Since both $$S_1$$ and $$S_2$$ simplify to the same expression $$\sim p \vee q \vee r$$, they are logically equivalent: $$S_1 \equiv S_2$$.
We now evaluate each option:
Option A: “If $$S_2$$ is True, then $$S_1$$ is True.” This holds because $$S_1 \equiv S_2$$.
Option B: “If $$S_2$$ is False, then $$S_1$$ is False.” This also holds by equivalence.
Option C: “If $$S_2$$ is False, then $$S_1$$ is True.” This would require different truth values for $$S_1$$ and $$S_2$$, contradicting their equivalence, so it is not true.
Option D: “If $$S_1$$ is False, then $$S_2$$ is False.” This holds by equivalence.
Therefore, the statement that is NOT true is Option C.
The statement $$(\sim(p \Leftrightarrow \sim q)) \wedge q$$ is:
We need to determine what the statement $$(\sim(p \Leftrightarrow \sim q)) \wedge q$$ is equivalent to.
$$p \Leftrightarrow \sim q$$ is true when p and $$\sim q$$ have the same truth value, i.e., when p and q have opposite truth values.
Therefore, $$\sim(p \Leftrightarrow \sim q)$$ is true when p and q have the same truth value, which means $$\sim(p \Leftrightarrow \sim q) \equiv (p \Leftrightarrow q)$$.
The statement becomes $$(p \Leftrightarrow q) \wedge q$$.
$$p = T, q = T$$: $$(T \Leftrightarrow T) \wedge T = T \wedge T = T$$
$$p = T, q = F$$: $$(T \Leftrightarrow F) \wedge F = F \wedge F = F$$
$$p = F, q = T$$: $$(F \Leftrightarrow T) \wedge T = F \wedge T = F$$
$$p = F, q = F$$: $$(F \Leftrightarrow F) \wedge F = T \wedge F = F$$
The statement is true only when $$p = T$$ and $$q = T$$, which is $$p \wedge q$$.
Option D: $$(p \Rightarrow q) \wedge p$$
$$p = T, q = T$$: $$T \wedge T = T$$
$$p = T, q = F$$: $$F \wedge T = F$$
$$p = F, q = T$$: $$T \wedge F = F$$
$$p = F, q = F$$: $$T \wedge F = F$$
This is also equivalent to $$p \wedge q$$. ✓
Therefore, the correct answer is Option D: equivalent to $$(p \Rightarrow q) \wedge p$$.
Consider the following statements:
$$A$$: Rishi is a judge.
$$B$$: Rishi is honest.
$$C$$: Rishi is not arrogant.
The negation of the statement "if Rishi is a judge and he is not arrogant, then he is honest" is
We are given the statements: $$A$$: Rishi is a judge, $$B$$: Rishi is honest, and $$C$$: Rishi is not arrogant.
The statement "if Rishi is a judge and he is not arrogant, then he is honest" can be written as: $$(A \wedge C) \to B$$
Recall that the negation of an implication $$p \to q$$ is $$p \wedge (\sim q)$$, so $$\sim[(A \wedge C) \to B] = (A \wedge C) \wedge (\sim B)$$.
This can be rewritten as: $$(\sim B) \wedge (A \wedge C)$$
Therefore, the negation is Option B: $$(\sim B) \wedge (A \wedge C)$$.
Consider the following two propositions :
$$P_1:\sim(p\to\sim q)$$
$$P_2:(p\land\sim q)\land(\sim p\lor q)$$
If the proposition $$p\to(\sim p\lor q) $$ is evaluated as FALSE, then
For an implication
$$A\to B$$
to be FALSE,
$$A=\text{TRUE},\qquad B=\text{FALSE}$$
Hence,
$$p=\text{TRUE}$$
and
$$\sim p\lor q=\text{FALSE}$$
Now, an OR statement is FALSE only when both parts are FALSE.
Therefore,
$$\sim p=\text{FALSE},\qquad q=\text{FALSE}$$
Thus,
$$p=\text{TRUE},\qquad q=\text{FALSE}$$
Now,
$$P_1=\sim(p\to\sim q)$$
Since
$$p=\text{TRUE},\qquad \sim q=\text{TRUE}$$
we get
$$p\to\sim q=\text{TRUE}$$
Hence,
$$P_1=\sim(\text{TRUE})=\text{FALSE}$$
Also,
$$P_2=(p\land\sim q)\land(\sim p\lor q)$$
$$=(\text{TRUE}\land\text{TRUE})\land(\text{FALSE}\lor\text{FALSE})$$
$$=\text{TRUE}\land\text{FALSE}$$
$$=\text{FALSE}$$
Therefore, both $$P_1$$ and $$P_2$$ are FALSE.
Let $$\Delta \in \{\wedge, \vee, \Rightarrow, \Leftrightarrow\}$$ be such that $$(p \wedge q)\Delta((p \vee q) \Rightarrow q)$$ is a tautology. Then $$\Delta$$ is equal to
We need to find $$\Delta \in \{\wedge, \vee, \Rightarrow, \Leftrightarrow\}$$ such that $$(p \wedge q) \;\Delta\; ((p \vee q) \Rightarrow q)$$ is a tautology.
Evaluate both components for all truth value combinations:
Let $$X = p \wedge q$$ and $$Y = (p \vee q) \Rightarrow q$$.
Case 1: $$p = T, q = T$$: $$X = T$$, $$p \vee q = T$$, $$Y = T \Rightarrow T = T$$. So $$T \;\Delta\; T$$.
Case 2: $$p = T, q = F$$: $$X = F$$, $$p \vee q = T$$, $$Y = T \Rightarrow F = F$$. So $$F \;\Delta\; F$$.
Case 3: $$p = F, q = T$$: $$X = F$$, $$p \vee q = T$$, $$Y = T \Rightarrow T = T$$. So $$F \;\Delta\; T$$.
Case 4: $$p = F, q = F$$: $$X = F$$, $$p \vee q = F$$, $$Y = F \Rightarrow F = T$$. So $$F \;\Delta\; T$$.
For a tautology, all four cases must give True:
From Case 1: $$T \;\Delta\; T = T$$ — true for all four connectives.
From Case 2: $$F \;\Delta\; F = T$$ — checking: $$\wedge$$: F, $$\vee$$: F, $$\Rightarrow$$: T, $$\Leftrightarrow$$: T. Only $$\Rightarrow$$ and $$\Leftrightarrow$$ work.
From Cases 3 and 4: $$F \;\Delta\; T = T$$ — checking: $$\Rightarrow$$: T, $$\Leftrightarrow$$: F. Only $$\Rightarrow$$ works.
Only $$\Delta = \Rightarrow$$ satisfies all cases.
The answer is Option C: $$\Rightarrow$$.
Let $$\Delta, \nabla \in \{\wedge, \vee\}$$ be such that $$p\nabla q \to ((p\Delta q)\nabla r)$$ is a tautology. Then $$(p\nabla q) \Delta r$$ is logically equivalent to
We need to find $$\Delta, \nabla \in \{\wedge, \vee\}$$ such that $$p \nabla q \to ((p \Delta q) \nabla r)$$ is a tautology, then determine what $$(p \nabla q) \Delta r$$ is logically equivalent to.
Since $$\nabla$$ and $$\Delta$$ can each be $$\vee$$ or $$\wedge$$, there are four possibilities. First, if $$\nabla = \vee$$ and $$\Delta = \vee$$, then $$p \vee q \to (p \vee q) \vee r$$. This is always true since $$(p \vee q) \vee r$$ contains $$p \vee q$$, so it is a tautology. Next, if $$\nabla = \vee$$ and $$\Delta = \wedge$$, then $$p \vee q \to (p \wedge q) \vee r$$. Taking $$p = T, q = F, r = F$$ yields $$T \to F$$, which is false, so this case is not a tautology. Now if $$\nabla = \wedge$$ and $$\Delta = \vee$$, then $$p \wedge q \to (p \vee q) \wedge r$$. Taking $$p = T, q = T, r = F$$ gives $$T \to F$$, which is false. Similarly, if $$\nabla = \wedge$$ and $$\Delta = \wedge$$, then $$p \wedge q \to (p \wedge q) \wedge r$$, and choosing the same values yields $$T \to F$$ again. Therefore the only tautology arises when $$\nabla = \vee$$ and $$\Delta = \vee$$.
Substituting these back shows that $$(p \nabla q) \Delta r$$ becomes $$(p \vee q) \vee r$$, which simplifies to $$p \vee q \vee r$$.
Among the answer choices, Option A: $$(p \Delta r) \vee q = (p \vee r) \vee q = p \vee q \vee r$$ matches this expression. The correct answer is Option A.
The correct answer is Option A.
Let $$r \in (P, q, \sim p, \sim q)$$ be such that the logical statement $$r \vee (\sim p) \Rightarrow (p \wedge q) \vee r$$ is a tautology. Then $$r$$ is equal to
First, we need to find $$r \in \{p, q, \sim p, \sim q\}$$ such that $$r \vee (\sim p) \Rightarrow (p \wedge q) \vee r$$ is a tautology.
Next, recall that an implication $$P \Rightarrow Q$$ is a tautology when $$Q$$ is true whenever $$P$$ is true. Therefore, we need: whenever $$r \vee (\sim p)$$ is true, $$(p \wedge q) \vee r$$ must also be true.
Now, test $$r = \sim p$$. The statement becomes:
$$ (\sim p) \vee (\sim p) \Rightarrow (p \wedge q) \vee (\sim p) $$
Substituting, this simplifies to:
$$ \sim p \Rightarrow (p \wedge q) \vee (\sim p) $$
Since the implication must hold in all cases, consider the following:
Case 1: $$p$$ is True (so $$\sim p$$ is False). The implication $$F \Rightarrow \text{anything}$$ is True.
Case 2: $$p$$ is False (so $$\sim p$$ is True). The RHS becomes $$(F \wedge q) \vee T = T$$. So $$T \Rightarrow T$$ is True.
Since the implication is true in all cases, it is a tautology. ✓
Next, verify that the other options fail.
For $$r = p$$: Let $$p = F, q = F$$. Then LHS: $$F \vee T = T$$, RHS: $$(F \wedge F) \vee F = F$$. So $$T \Rightarrow F$$ is False. ✗
For $$r = q$$: Let $$p = F, q = F$$. Then LHS: $$F \vee T = T$$, RHS: $$(F \wedge F) \vee F = F$$. So $$T \Rightarrow F$$ is False. ✗
For $$r = \sim q$$: Let $$p = T, q = T$$. Then LHS: $$F \vee F = F$$, so implication is True. Let $$p = F, q = T$$. Then LHS: $$F \vee T = T$$, RHS: $$(F \wedge T) \vee F = F$$. So $$T \Rightarrow F$$ is False. ✗
Therefore, the answer is Option C: $$\sim p$$.
The boolean expression $$(\sim(p \wedge q)) \vee q$$ is equivalent to
We need to find the expression equivalent to $$(\sim(p \wedge q)) \vee q$$.
Using De Morgan's law: $$\sim(p \wedge q) = \sim p \vee \sim q$$. Substituting gives $$(\sim(p \wedge q)) \vee q = (\sim p \vee \sim q) \vee q = \sim p \vee (\sim q \vee q) = \sim p \vee T = T$$ (since $$\sim q \vee q$$ is always true), so the original expression is a tautology.
Next, we examine each option:
Option A: $$q \to (p \wedge q) = \sim q \vee (p \wedge q) = (\sim q \vee p) \wedge (\sim q \vee q) = (\sim q \vee p) \wedge T = \sim q \vee p$$. This is NOT always true (fails when $$p = F, q = T$$), so it is not a tautology.
Option B: $$p \to q = \sim p \vee q$$. This is NOT always true (fails when $$p = T, q = F$$), so it is not a tautology.
Option C: $$p \to (p \to q) = p \to (\sim p \vee q) = \sim p \vee (\sim p \vee q) = \sim p \vee q$$. This is the same as Option B and thus not a tautology.
Option D: $$p \to (p \vee q) = \sim p \vee (p \vee q) = (\sim p \vee p) \vee q = T \vee q = T$$. This is always true — a tautology.
Since the given expression simplifies to a tautology, and Option D is also a tautology, they are logically equivalent.
The correct answer is Option D.
The statement $$(p \wedge q) \Rightarrow (p \wedge r)$$ is equivalent to
We need to determine which statement is equivalent to $$(p \wedge q) \Rightarrow (p \wedge r)$$.
We begin by rewriting the implication using the identity $$A \Rightarrow B \equiv \neg A \vee B$$. We have $$(p \wedge q) \Rightarrow (p \wedge r) \equiv \neg(p \wedge q) \vee (p \wedge r) \equiv (\neg p \vee \neg q) \vee (p \wedge r)$$.
Now let us examine Option D: $$(p \wedge q) \Rightarrow r \equiv \neg(p \wedge q) \vee r \equiv (\neg p \vee \neg q) \vee r$$.
We claim these two expressions are logically equivalent. To verify, we check all cases based on $$p$$.
Case 1: If $$p$$ is false, then $$\neg p$$ is true, so both $$(\neg p \vee \neg q) \vee (p \wedge r)$$ and $$(\neg p \vee \neg q) \vee r$$ evaluate to true regardless of $$q$$ and $$r$$.
Case 2: If $$p$$ is true and $$q$$ is false, then $$\neg q$$ is true, so both expressions again evaluate to true.
Case 3: If $$p$$ is true and $$q$$ is true, then $$\neg p \vee \neg q = \text{false}$$. The first expression becomes $$(p \wedge r) = r$$ (since $$p$$ is true), and the second becomes simply $$r$$. Hence both equal $$r$$.
In every case the two expressions agree, confirming that $$(p \wedge q) \Rightarrow (p \wedge r) \equiv (p \wedge q) \Rightarrow r$$.
Hence, the correct answer is Option D.
Which of the following statements is a tautology?
We need to determine which of the given statements is a tautology (always true regardless of truth values of $$ p $$ and $$ q $$).
Recall that $$ A \Rightarrow B $$ is equivalent to $$ \sim A \lor B $$.
$$q \Rightarrow (\sim p \lor q) \equiv \sim q \lor (\sim p \lor q) \equiv \sim p \lor (\sim q \lor q) \equiv \sim p \lor T \equiv T$$
Since $$ \sim q \lor q $$ is always true (law of excluded middle), the entire expression simplifies to True. This is a tautology.
Option A: $$ (\sim p \lor q) \Rightarrow p \equiv \sim(\sim p \lor q) \lor p \equiv (p \land \sim q) \lor p \equiv p $$. This is not a tautology (false when $$ p = F $$).
Option B: $$ p \Rightarrow (\sim p \lor q) \equiv \sim p \lor (\sim p \lor q) \equiv \sim p \lor q $$. This is not a tautology (false when $$ p = T, q = F $$).
Option C: $$ (\sim p \lor q) \Rightarrow q \equiv \sim(\sim p \lor q) \lor q \equiv (p \land \sim q) \lor q \equiv (p \lor q) \land (\sim q \lor q) \equiv p \lor q $$. This is not a tautology (false when $$ p = F, q = F $$).
The tautology is $$ q \Rightarrow (\sim p \lor q) $$, which corresponds to Option D.
If the truth value of the statement $$(P \wedge (\sim R)) \to ((\sim R) \wedge Q)$$ is F, then the truth value of which of the following is F?
The statement $$(P \wedge (\sim R)) \to ((\sim R) \wedge Q)$$ is given to be False. An implication $$p \to q$$ is false only when $$p$$ is True and $$q$$ is False, so we require $$P \wedge (\sim R) = T$$ and $$(\sim R) \wedge Q = F$$. From $$P \wedge (\sim R) = T$$ we deduce $$P = T$$ and $$\sim R = T$$, hence $$R = F$$. Since $$(\sim R) \wedge Q = F$$ and $$\sim R = T$$, it follows that $$Q = F$$. Therefore $$P = T,\ Q = F,\ R = F$$.
Substituting these truth values into each option, we find:
Option A: $$P \vee Q \to \sim R = (T \vee F) \to T = T \to T = T$$
Option B: $$R \vee Q \to \sim P = (F \vee F) \to F = F \to F = T$$
Option C: $$\sim(P \vee Q) \to \sim R = \sim(T) \to T = F \to T = T$$
Option D: $$\sim(R \vee Q) \to \sim P = \sim(F) \to F = T \to F = F$$
The statement with truth value False is $$\boxed{\sim(R \vee Q) \to \sim P}$$, so the answer is Option D.
Let the operations $$*, \odot \in \{\wedge, \vee\}$$. If $$(p * q) \odot (p \odot \sim q)$$ is a tautology, then the ordered pair $$(*, \odot)$$ is
We need to find the ordered pair $$(*, \odot)$$ from $$\{\wedge, \vee\}$$ such that $$(p * q) \odot (p \odot \sim q)$$ is a tautology.
Step 1: Test each option systematically.
Option B: $$(*, \odot) = (\vee, \vee)$$
The expression becomes: $$(p \vee q) \vee (p \vee \sim q)$$
$$= p \vee q \vee p \vee \sim q$$
$$= p \vee (q \vee \sim q)$$
$$= p \vee T$$
$$= T$$
This is a tautology.
Step 2: Verify that other options are not tautologies.
Option A: $$(*, \odot) = (\vee, \wedge)$$
$$(p \vee q) \wedge (p \wedge \sim q)$$
When $$p = F, q = T$$: $$(F \vee T) \wedge (F \wedge F) = T \wedge F = F$$. Not a tautology.
Option C: $$(*, \odot) = (\wedge, \wedge)$$
$$(p \wedge q) \wedge (p \wedge \sim q)$$
$$= p \wedge (q \wedge \sim q) = p \wedge F = F$$. Not a tautology (always false).
Option D: $$(*, \odot) = (\wedge, \vee)$$
$$(p \wedge q) \vee (p \vee \sim q)$$
When $$p = F, q = T$$: $$(F \wedge T) \vee (F \vee F) = F \vee F = F$$. Not a tautology.
Only Option B gives a tautology.
The correct answer is Option B: $$(\vee, \vee)$$
The number of choices for $$\Delta \in \{\wedge, \vee, \Rightarrow, \Leftrightarrow\}$$, such that $$(p \Delta q) \Rightarrow ((p \Delta \sim q) \vee ((\sim p) \Delta q))$$ is a tautology, is
We need to find how many choices for $$\Delta \in \{\wedge, \vee, \Rightarrow, \Leftrightarrow\}$$ make $$(p \Delta q) \Rightarrow ((p \Delta \sim q) \vee ((\sim p) \Delta q))$$ a tautology.
Recall that $$P \Rightarrow Q$$ is false only when $$P$$ is true and $$Q$$ is false. So the expression is a tautology if whenever $$(p \Delta q)$$ is true, at least one of $$(p \Delta \sim q)$$ or $$(\sim p \Delta q)$$ is also true.
Case 1: $$\Delta = \wedge$$ (AND)
$$(p \wedge q) \Rightarrow ((p \wedge \sim q) \vee (\sim p \wedge q))$$
When $$p = T, q = T$$: LHS = T. RHS = $$(T \wedge F) \vee (F \wedge T) = F \vee F = F$$.
So the implication is F. Not a tautology.
Case 2: $$\Delta = \vee$$ (OR)
$$(p \vee q) \Rightarrow ((p \vee \sim q) \vee (\sim p \vee q))$$
RHS: $$(p \vee \sim q) \vee (\sim p \vee q) = (p \vee \sim p) \vee (q \vee \sim q) = T \vee T = T$$.
Since RHS is always T, the implication is always T. Tautology.
Case 3: $$\Delta = \Rightarrow$$ (Implication)
$$(p \Rightarrow q) \Rightarrow ((p \Rightarrow \sim q) \vee (\sim p \Rightarrow q))$$
$$(\sim p \Rightarrow q)$$ is equivalent to $$(p \vee q)$$. This is false only when $$p = F, q = F$$.
When $$p = F, q = F$$: LHS = $$(F \Rightarrow F) = T$$. RHS = $$(F \Rightarrow T) \vee (T \Rightarrow F) = T \vee F = T$$.
When $$p = T, q = T$$: LHS = T. RHS = $$(T \Rightarrow F) \vee (F \Rightarrow T) = F \vee T = T$$.
When $$p = T, q = F$$: LHS = F. So implication is T.
When $$p = F, q = T$$: LHS = T. RHS = $$(F \Rightarrow F) \vee (T \Rightarrow T) = T \vee T = T$$.
All cases give T. Tautology.
Case 4: $$\Delta = \Leftrightarrow$$ (Biconditional)
$$(p \Leftrightarrow q) \Rightarrow ((p \Leftrightarrow \sim q) \vee (\sim p \Leftrightarrow q))$$
Note: $$(p \Leftrightarrow \sim q) = \sim(p \Leftrightarrow q)$$ and $$(\sim p \Leftrightarrow q) = \sim(p \Leftrightarrow q)$$.
So RHS = $$\sim(p \Leftrightarrow q) \vee \sim(p \Leftrightarrow q) = \sim(p \Leftrightarrow q)$$.
The expression becomes: $$(p \Leftrightarrow q) \Rightarrow \sim(p \Leftrightarrow q)$$.
When $$p = T, q = T$$: $$(T) \Rightarrow (F) = F$$. Not a tautology.
Therefore, exactly 2 choices ($$\vee$$ and $$\Rightarrow$$) make the expression a tautology.
The answer is Option B: 2.
The statement $$(p \Rightarrow q) \vee (p \Rightarrow r)$$ is NOT equivalent to:
We need to determine which statement is NOT equivalent to $$(p \Rightarrow q) \vee (p \Rightarrow r)$$.
We first simplify the given statement. We know $$p \Rightarrow q \equiv \sim p \vee q$$ and $$p \Rightarrow r \equiv \sim p \vee r$$. So $$(p \Rightarrow q) \vee (p \Rightarrow r) \equiv (\sim p \vee q) \vee (\sim p \vee r) \equiv \sim p \vee q \vee r$$. This is equivalent to $$p \Rightarrow (q \vee r)$$.
Now we check each option:
Option A: $$(p \wedge \sim r) \Rightarrow q \equiv \sim(p \wedge \sim r) \vee q \equiv \sim p \vee r \vee q$$. This equals $$\sim p \vee q \vee r$$. Equivalent.
Option B: $$\sim q \Rightarrow (\sim r \vee p) \equiv q \vee \sim r \vee p$$. This is $$p \vee q \vee \sim r$$, which is NOT the same as $$\sim p \vee q \vee r$$. For example, when $$p = T, q = F, r = T$$: our expression gives $$F \vee F \vee T = T$$, but Option B gives $$T \vee F \vee F = T$$. Try $$p = T, q = F, r = F$$: our expression gives $$F \vee F \vee F = F$$, but Option B gives $$T \vee F \vee T = T$$. So they differ. NOT equivalent.
Option C: $$p \Rightarrow (q \vee r) \equiv \sim p \vee q \vee r$$. Equivalent (same as our simplified form).
Option D: $$(p \wedge \sim q) \Rightarrow r \equiv \sim(p \wedge \sim q) \vee r \equiv \sim p \vee q \vee r$$. Equivalent.
Hence, the correct answer is Option B: $$\sim q \Rightarrow (\sim r \vee p)$$.
Which of the following statement is a tautology?
We need to identify which of the given statements is a tautology (always true regardless of truth values of $$p$$ and $$q$$).
Analyze Option A: $$((\sim q) \wedge p) \wedge q$$
This simplifies to $$p \wedge q \wedge (\sim q)$$, which contains $$q \wedge (\sim q) = F$$.
So this is always False (contradiction). Not a tautology.
Analyze Option B: $$((\sim q) \wedge p) \wedge (p \wedge (\sim p))$$
The term $$p \wedge (\sim p) = F$$.
So the entire expression is $$(\text{anything}) \wedge F = F$$.
This is always False (contradiction). Not a tautology.
Analyze Option C: $$((\sim q) \wedge p) \vee (p \vee (\sim p))$$
The term $$p \vee (\sim p) = T$$ (this is a tautology by itself).
So the entire expression is $$(\text{anything}) \vee T = T$$.
This is always True. This is a tautology!
Analyze Option D: $$(p \wedge q) \wedge (\sim(p \wedge q))$$
Let $$r = p \wedge q$$. Then this becomes $$r \wedge (\sim r) = F$$.
This is always False (contradiction). Not a tautology.
Therefore, the tautology is Option C: $$((\sim q) \wedge p) \vee (p \vee (\sim p))$$.
The correct answer is Option C.
Negation of the Boolean expression $$p \leftrightarrow (q \rightarrow p)$$ is
We need to find the negation of the Boolean expression $$p \leftrightarrow (q \rightarrow p)$$.
$$q \rightarrow p \equiv \sim q \vee p$$
$$p \leftrightarrow (\sim q \vee p) \equiv [p \rightarrow (\sim q \vee p)] \wedge [(\sim q \vee p) \rightarrow p]$$
The first part: $$p \rightarrow (\sim q \vee p) \equiv \sim p \vee \sim q \vee p \equiv T$$ (tautology, since $$\sim p \vee p = T$$)
So: $$p \leftrightarrow (\sim q \vee p) \equiv T \wedge [(\sim q \vee p) \rightarrow p] \equiv (\sim q \vee p) \rightarrow p$$
$$(\sim q \vee p) \rightarrow p \equiv \sim(\sim q \vee p) \vee p \equiv (q \wedge \sim p) \vee p$$
$$\equiv (q \vee p) \wedge (\sim p \vee p) \equiv (q \vee p) \wedge T \equiv q \vee p \equiv p \vee q$$
So $$p \leftrightarrow (q \rightarrow p) \equiv p \vee q$$.
$$\sim(p \vee q) \equiv \sim p \wedge \sim q$$
| $$p$$ | $$q$$ | $$q \rightarrow p$$ | $$p \leftrightarrow (q \rightarrow p)$$ | Negation |
|---|---|---|---|---|
| T | T | T | T | F |
| T | F | T | T | F |
| F | T | F | T | F |
| F | F | T | F | T |
The negation is T only when both $$p$$ and $$q$$ are F, which is $$\sim p \wedge \sim q$$. $$\checkmark$$
Therefore, the correct answer is Option D: $$\sim p \wedge \sim q$$.
Negation of the Boolean statement $$(p \vee q) \Rightarrow ((\sim r) \vee p)$$ is equivalent to:
We need to find the negation of $$(p \vee q) \Rightarrow ((\sim r) \vee p)$$. The negation of $$A \Rightarrow B$$ is $$A \wedge (\sim B)$$. Here $$A = (p \vee q)$$ and $$B = ((\sim r) \vee p)$$, so its negation is $$(p \vee q) \wedge \sim((\sim r) \vee p)$$.
By De Morgan's law, $$\sim((\sim r) \vee p) = r \wedge (\sim p)$$, therefore the expression becomes $$(p \vee q) \wedge r \wedge (\sim p)$$. Since $$\sim p$$ holds, $$(p \vee q) \wedge (\sim p)$$ simplifies to $$q \wedge (\sim p)$$, giving $$(\sim p) \wedge q \wedge r$$.
Therefore, the answer is Option C: $$(\sim p) \wedge q \wedge r$$.
Consider the following statements:
$$P$$: Ramu is intelligent.
$$Q$$: Ramu is rich.
$$R$$: Ramu is not honest.
The negation of the statement "Ramu is intelligent and honest if and only if Ramu is not rich" can be expressed as:
We are given: $$P$$: Ramu is intelligent, $$Q$$: Ramu is rich, $$R$$: Ramu is not honest. So "Ramu is honest" is $$\sim R$$.
The statement "Ramu is intelligent and honest if and only if Ramu is not rich" translates to $$(P \wedge \sim R) \leftrightarrow (\sim Q)$$.
The negation of a biconditional is: $$\sim(A \leftrightarrow B) = (A \wedge \sim B) \vee (\sim A \wedge B)$$.
Here $$A = P \wedge (\sim R)$$ and $$B = \sim Q$$.
The first part: $$A \wedge \sim B = (P \wedge (\sim R)) \wedge Q$$.
The second part: $$\sim A \wedge B = \sim(P \wedge (\sim R)) \wedge (\sim Q) = ((\sim P) \vee R) \wedge (\sim Q)$$.
The full negation is $$((P \wedge (\sim R)) \wedge Q) \vee (((\sim P) \vee R) \wedge (\sim Q))$$.
The answer is Option D: $$((P \wedge (\sim R)) \wedge Q) \vee ((\sim Q) \wedge ((\sim P) \vee R))$$.
Let a function $$f : \mathbb{N} \to \mathbb{N}$$ be defined by
$$f(n) = \begin{cases} 2n, & n = 2, 4, 6, 8, \ldots \\ n-1, & n = 3, 7, 11, 15, \ldots \\ \frac{n+1}{2}, & n = 1, 5, 9, 13, \ldots \end{cases}$$
then, $$f$$ is
The function $$f : \mathbb{N} \to \mathbb{N}$$ is defined as:
$$f(n) = \begin{cases} 2n, & n = 2, 4, 6, 8, \ldots \text{ (even numbers)} \\ n-1, & n = 3, 7, 11, 15, \ldots \text{ (} n \equiv 3 \pmod{4}\text{)} \\ \frac{n+1}{2}, & n = 1, 5, 9, 13, \ldots \text{ (} n \equiv 1 \pmod{4}\text{)} \end{cases}$$
For even inputs $$n = 2,4,6,\ldots$$, we have $$f(n)=2n$$, which yields $$4,8,12,16,\ldots$$—all multiples of 4, i.e.\ $$\{n\in\mathbb{N}:n\equiv0\pmod4\}$$. If $$n\equiv3\pmod4$$ (so $$n=3,7,11,\ldots$$), then $$f(n)=n-1$$ gives $$2,6,10,14,\ldots$$—the set $$\{n\in\mathbb{N}:n\equiv2\pmod4\}$$. Finally, if $$n\equiv1\pmod4$$ (so $$n=1,5,9,\ldots$$), then $$f(n)=\frac{n+1}{2}$$ produces $$1,3,5,7,\ldots$$—all odd natural numbers.
Thus the range of $$f$$ is $$\{1,3,5,7,\ldots\}\cup\{2,6,10,14,\ldots\}\cup\{4,8,12,16,\ldots\}=\{\text{odd numbers}\}\cup\{\text{numbers}\equiv2\pmod4\}\cup\{\text{multiples of }4\}=\mathbb{N},$$ so $$f$$ is onto.
The three output sets—odd numbers, numbers congruent to 2 mod 4, and multiples of 4—are mutually disjoint, and in each case the rule is strictly increasing (hence injective). Therefore $$f$$ is one-one as well.
Therefore, the correct answer is Option A: One-one and onto.
Let $$f: \mathbb{R} \to \mathbb{R}$$ be a continuous function such that $$f(3x) - f(x) = x$$. If $$f(8) = 7$$, then $$f(14)$$ is equal to:
We have $$f: \mathbb{R} \to \mathbb{R}$$ continuous, with $$f(3x) - f(x) = x$$, $$f(8) = 7$$.
Let $$f(x) = ax + b$$. Then:
$$f(3x) - f(x) = 3ax + b - ax - b = 2ax = x$$
$$\implies a = \frac{1}{2}$$
So $$f(x) = \frac{x}{2} + b$$.
$$f(8) = \frac{8}{2} + b = 4 + b = 7 \implies b = 3$$
$$f(x) = \frac{x}{2} + 3$$
$$f(14) = \frac{14}{2} + 3 = 7 + 3 = 10$$
Verification: $$f(3 \times 14) - f(14) = f(42) - f(14) = (21 + 3) - (7 + 3) = 24 - 10 = 14$$ ✓
Therefore, the correct answer is Option B: 10.
The negation of the Boolean expression $$\sim q \wedge p \Rightarrow \sim p \vee q$$ is logically equivalent to
Given statement,
$$\sim q\land p\Rightarrow \sim p\lor q$$
Now,
$$\sim p\lor q\equiv p\Rightarrow q$$
and
$$\sim q\land p\equiv \sim(p\Rightarrow q)$$
Therefore, the statement becomes
$$\sim(p\Rightarrow q)\Rightarrow (p\Rightarrow q)$$
Let
$$A=(p\Rightarrow q)$$
Then the statement is
$$\sim A\Rightarrow A$$
The negation of
$$\sim A\Rightarrow A$$
is
$$\sim A\land \sim A$$
$$=\sim A$$
Substituting back,
$$=\sim(p\Rightarrow q)$$
Hence, the required negation is $$\boxed{\sim(p\Rightarrow q)}$$.
The total number of functions, $$f: \{1, 2, 3, 4\} \to \{1, 2, 3, 4, 5, 6\}$$ such that $$f(1) + f(2) = f(3)$$, is equal to
We need to count the total number of functions $$ f: \{1, 2, 3, 4\} \to \{1, 2, 3, 4, 5, 6\} $$ such that $$ f(1) + f(2) = f(3) $$.
We need $$ f(1) + f(2) = f(3) $$, where $$ f(1), f(2) \in \{1, 2, 3, 4, 5, 6\} $$ and $$ f(3) \in \{1, 2, 3, 4, 5, 6\} $$.
So we need $$ 2 \le f(1) + f(2) \le 6 $$ (since both are at least 1, and the sum must be at most 6).
Count pairs $$ (f(1), f(2)) $$ for each value of $$ f(3) $$:
- $$ f(3) = 2 $$: $$ f(1) + f(2) = 2 $$: only $$ (1,1) $$ — 1 pair
- $$ f(3) = 3 $$: $$ f(1) + f(2) = 3 $$: $$ (1,2), (2,1) $$ — 2 pairs
- $$ f(3) = 4 $$: $$ f(1) + f(2) = 4 $$: $$ (1,3), (2,2), (3,1) $$ — 3 pairs
- $$ f(3) = 5 $$: $$ f(1) + f(2) = 5 $$: $$ (1,4), (2,3), (3,2), (4,1) $$ — 4 pairs
- $$ f(3) = 6 $$: $$ f(1) + f(2) = 6 $$: $$ (1,5), (2,4), (3,3), (4,2), (5,1) $$ — 5 pairs
Total valid triples = $$ 1 + 2 + 3 + 4 + 5 = 15 $$.
$$ f(4) $$ can be any value in $$ \{1, 2, 3, 4, 5, 6\} $$, so there are 6 choices.
$$\text{Total} = 15 \times 6 = 90$$
The total number of functions is 90, which corresponds to Option B.
Let $$f : \mathbb{R} \to \mathbb{R}$$ be defined as $$f(x) = x - 1$$ and $$g : R \to \{1, -1\} \to \mathbb{R}$$ be defined as $$g(x) = \frac{x^2}{x^2 - 1}$$. Then the function $$fog$$ is:
We need to determine whether $$f \circ g$$ is one-one and/or onto, where $$f : \mathbb{R} \to \mathbb{R}$$ is defined as $$f(x) = x - 1$$ and $$g : \mathbb{R} \setminus \{1, -1\} \to \mathbb{R}$$ is defined as $$g(x) = \frac{x^2}{x^2 - 1}$$.
First, we find the composite function. The domain of $$f \circ g$$ is the domain of $$g$$, which is $$\mathbb{R} \setminus \{-1, 1\}$$, and the codomain is $$\mathbb{R}$$. Substituting gives $$f(g(x)) = g(x) - 1 = \frac{x^2}{x^2 - 1} - 1 = \frac{x^2 - (x^2 - 1)}{x^2 - 1} = \frac{1}{x^2 - 1}.$$
Next, we check if $$f \circ g$$ is one-one (injective) by testing whether $$f(g(x_1)) = f(g(x_2))$$ implies $$x_1 = x_2$$. Since $$f(g(x)) = \frac{1}{x^2 - 1}$$ depends only on $$x^2$$, we have $$f(g(x)) = f(g(-x))$$ for all $$x$$ in the domain. For example, take $$x = 2$$ and $$x = -2$$: $$f(g(2)) = \frac{1}{4 - 1} = \frac{1}{3}, \quad f(g(-2)) = \frac{1}{4 - 1} = \frac{1}{3}.$$ Since $$2 \neq -2$$ but $$f(g(2)) = f(g(-2))$$, the function is not one-one.
Now, we check if $$f \circ g$$ is onto (surjective). We need to determine whether every real number $$y$$ is in the range of $$h(x) = \frac{1}{x^2 - 1}$$. Setting $$y = \frac{1}{x^2 - 1}$$ gives $$x^2 - 1 = \frac{1}{y}, \quad x^2 = 1 + \frac{1}{y}.$$ For a real solution to exist, we need $$y \neq 0$$ and $$1 + \frac{1}{y} \geq 0$$, i.e., $$\frac{y + 1}{y} \geq 0.$$ Therefore, such values of $$y$$ satisfy $$y > 0$$ or $$y \leq -1$$ (and additionally $$x \neq \pm 1$$, which means $$x^2 \neq 1$$, i.e., $$\frac{1}{y} \neq 0$$, which is always true).
Case-by-case analysis of values NOT in the range:
Case 1: $$y = 0$$. Since $$\frac{1}{x^2 - 1} = 0$$ has no solution, $$y = 0$$ is not in the range.
Case 2: $$-1 < y < 0$$. Here $$\frac{y + 1}{y} < 0$$, so $$x^2 < 0$$, which gives no real solution. These values are not in the range. For instance, $$y = -\frac{1}{2}$$ gives $$x^2 = 1 - 2 = -1 < 0$$, which has no real solution.
Since not every real number is achieved (the interval $$(-1, 0]$$ is not in the range), the function is not onto.
Therefore, $$f \circ g$$ is neither one-one nor onto.
The answer is Option D: Neither one-one nor onto.
Let $$f : N \to R$$ be a function such that $$f(x + y) = 2f(x)f(y)$$ for natural numbers $$x$$ and $$y$$. If $$f(1) = 2$$, then the value of $$\alpha$$ for which $$\sum_{k=1}^{10} f(\alpha + k) = \frac{512}{3}2^{20} - 1$$ holds, is
We need to find $$\alpha$$ such that $$\sum_{k=1}^{10}f(\alpha + k)=\frac{512}{3}(2^{20}-1)\,.$$
First, observe that $$f(x+y)=2f(x)f(y)$$ with $$f(1)=2$$. Substituting $$x=y=1$$ gives $$f(2)=2f(1)^2=2\times4=8=2^3$$, and then for $$x=1,y=2$$ we get $$f(3)=2f(1)f(2)=2\times2\times8=32=2^5$$. Likewise, $$x=1,y=3$$ yields $$f(4)=2f(1)f(3)=2\times2\times32=128=2^7$$, so by induction the pattern is $$f(n)=2^{2n-1}$$, which indeed satisfies $$f(x+y)=2^{2(x+y)-1}=2\cdot2^{2x-1}\cdot2^{2y-1}=2f(x)f(y)\,. $$
Since $$f(n)=2^{2n-1}$$, the sum becomes $$\sum_{k=1}^{10}f(\alpha + k)=\sum_{k=1}^{10}2^{2(\alpha+k)-1}=2^{2\alpha-1}\sum_{k=1}^{10}2^{2k}=2^{2\alpha-1}\sum_{k=1}^{10}4^k$$ which simplifies to $$2^{2\alpha-1}\cdot\frac{4(4^{10}-1)}{4-1}=2^{2\alpha-1}\cdot\frac{4(2^{20}-1)}{3}\,.$$
Equating this to $$\frac{512}{3}(2^{20}-1)$$ gives $$2^{2\alpha-1}\cdot\frac{4(2^{20}-1)}{3}=\frac{512}{3}(2^{20}-1)\,, $$ hence $$2^{2\alpha-1}\cdot4=512\,, $$ or $$2^{2\alpha-1}\cdot2^2=2^9\,, $$ so $$2^{2\alpha+1}=2^9$$ and therefore $$2\alpha+1=9\implies\alpha=4\,. $$
Thus the correct answer is $$4$$.
Let $$f(x) = \frac{x-1}{x+1}, x \in R - \{0, -1, 1\}$$. If $$f^{n+1}(x) = f(f^n(x))$$ for all $$n \in N$$, then $$f^6(6) + f^7(7)$$ is equal to
We need to find $$f^6(6) + f^7(7)$$ where $$f(x) = \frac{x-1}{x+1}$$.
Since $$f^1(x) = \frac{x-1}{x+1}$$, a calculation shows $$f^2(x) = f(f(x)) = \frac{\frac{x-1}{x+1} - 1}{\frac{x-1}{x+1} + 1} = \frac{x - 1 - x - 1}{x - 1 + x + 1} = \frac{-2}{2x} = -\frac{1}{x}$$.
Then applying the function again gives $$f^3(x) = f\left(-\frac{1}{x}\right) = \frac{-\frac{1}{x} - 1}{-\frac{1}{x} + 1} = \frac{-1 - x}{-1 + x} = -\frac{x + 1}{x - 1}$$, and one more iteration yields $$f^4(x) = f\left(-\frac{x+1}{x-1}\right) = \frac{-\frac{x+1}{x-1} - 1}{-\frac{x+1}{x-1} + 1} = \frac{-x-1-x+1}{-x-1+x-1} = \frac{-2x}{-2} = x$$.
Therefore, the function has period 4: $$f^4(x) = x$$.
Now reducing the exponents modulo 4 gives $$f^6 = f^{4+2} = f^2$$ and $$f^7 = f^{4+3} = f^3$$.
Substituting these into the arguments yields $$f^6(6) = f^2(6) = -\frac{1}{6}$$ and $$f^7(7) = f^3(7) = -\frac{7+1}{7-1} = -\frac{8}{6} = -\frac{4}{3}$$.
From this it follows that $$f^6(6) + f^7(7) = -\frac{1}{6} - \frac{4}{3} = -\frac{1}{6} - \frac{8}{6} = -\frac{9}{6} = -\frac{3}{2}$$.
The correct answer is Option B.
The domain of the function $$f(x) = \sin^{-1}[2x^2 - 3] + \log_2\left(\log_{\frac{1}{2}}(x^2 - 5x + 5)\right)$$, where $$[t]$$ is the greatest integer function, is
Given,
$$f(x)=\sin^{-1}[2x^2-3]+\log_2\left(\log_{\frac12}(x^2-5x+5)\right)$$
For the function to exist, both parts must be defined.
First consider
$$\sin^{-1}[2x^2-3]$$
Since $$\sin^{-1}t$$ is defined for $$-1\le t\le1,$$
we need $$-1\le[2x^2-3]\le1$$
As the GIF gives only integers,
$$[2x^2-3]\in\{-1,0,1\}$$
Hence,
$$-1\le2x^2-3<2$$
$$2\le2x^2<5$$
$$1\le x^2<\frac52$$
Therefore,
$$x\in\left(-\sqrt{\frac52},-1\right]\cup\left[1,\sqrt{\frac52}\right)$$
Now consider
$$\log_2\left(\log_{\frac12}(x^2-5x+5)\right)$$
For the outer logarithm,
$$\log_{\frac12}(x^2-5x+5)>0$$
Since the base
$$\frac12<1,$$
$$\log_{\frac12}t>0\iff0<t<1$$
Thus,
$$0<x^2-5x+5<1$$
Now solve separately.
From $$x^2-5x+5>0,$$
roots are $$x=\frac{5\pm\sqrt5}{2}$$
Hence,
$$x\in\left(-\infty,\frac{5-\sqrt5}{2}\right)\cup\left(\frac{5+\sqrt5}{2},\infty\right)$$
Also,
$$x^2-5x+5<1$$
$$x^2-5x+4<0$$
$$(x-1)(x-4)<0$$
$$1<x<4$$
Combining both,
$$x\in\left(1,\frac{5-\sqrt5}{2}\right)\cup\left(\frac{5+\sqrt5}{2},4\right)$$
Now intersect with
$$x\in\left(-\sqrt{\frac52},-1\right]\cup\left[1,\sqrt{\frac52}\right)$$
Since
$$\sqrt{\frac52}<\frac{5+\sqrt5}{2},$$
only the first interval survives.
Therefore, the domain is
$$\boxed{\left(1,\frac{5-\sqrt5}{2}\right)}$$.
Let $$\alpha, \beta$$ and $$\gamma$$ be three positive real numbers. Let $$f(x) = \alpha x^5 + \beta x^3 + \gamma x$$, $$x \in \mathbb{R}$$ and $$g: \mathbb{R} \to \mathbb{R}$$ be such that $$g(f(x)) = x$$ for all $$x \in \mathbb{R}$$. If $$a_1, a_2, a_3, \ldots, a_n$$ be in arithmetic progression with mean zero, then the value of $$f\left(g\left(\frac{1}{n}\sum_{i=1}^{n} f(a_i)\right)\right)$$ is equal to
We need to find $$f\left(g\left(\frac{1}{n}\sum_{i=1}^{n} f(a_i)\right)\right)$$ where $$a_1, a_2, \ldots, a_n$$ are in AP with mean zero.
Step 1: Understand the given functions.
$$f(x) = \alpha x^5 + \beta x^3 + \gamma x$$ where $$\alpha, \beta, \gamma > 0$$.
$$g(f(x)) = x$$ for all $$x \in \mathbb{R}$$, so $$g = f^{-1}$$ ($$g$$ is the inverse function of $$f$$).
Step 2: Observe that $$f$$ is an odd function.
$$f(-x) = \alpha(-x)^5 + \beta(-x)^3 + \gamma(-x) = -\alpha x^5 - \beta x^3 - \gamma x = -f(x)$$
So $$f$$ is an odd function: $$f(-x) = -f(x)$$.
Step 3: Use the AP with mean zero property.
Since $$a_1, a_2, \ldots, a_n$$ are in AP with mean zero:
$$\frac{1}{n}\sum_{i=1}^{n} a_i = 0$$
The terms are symmetric about zero, meaning they can be paired as $$a_i$$ and $$a_{n+1-i} = -a_i$$.
Step 4: Evaluate $$\sum f(a_i)$$.
Since the $$a_i$$ are symmetric about 0 and $$f$$ is odd:
$$f(a_i) + f(a_{n+1-i}) = f(a_i) + f(-a_i) = f(a_i) - f(a_i) = 0$$
Each pair sums to zero. If $$n$$ is odd, the middle term is $$a_{(n+1)/2} = 0$$, and $$f(0) = 0$$.
Therefore: $$\sum_{i=1}^{n} f(a_i) = 0$$
Step 5: Compute the final expression.
$$\frac{1}{n}\sum_{i=1}^{n} f(a_i) = \frac{0}{n} = 0$$
$$g(0) = ?$$ Since $$f(0) = 0$$, and $$g = f^{-1}$$, we get $$g(0) = 0$$.
$$f(g(0)) = f(0) = 0$$
The correct answer is Option A: $$0$$
The domain of $$f(x) = \frac{\cos^{-1}\left(\frac{x^2 - 5x + 6}{x^2 - 9}\right)}{\log(x^2 - 3x + 2)}$$ is
Given,
$$f(x)=\frac{\cos^{-1}\left(\dfrac{x^2-5x+6}{x^2-9}\right)}{\log(x^2-3x+2)}$$
For the function to be defined, we need:
1. $$-1\le \dfrac{x^2-5x+6}{x^2-9}\le1$$
2. $$x^2-3x+2>0$$
3. $$\log(x^2-3x+2)\ne0$$
4. $$x^2-9\ne0$$
Now,
$$\frac{x^2-5x+6}{x^2-9}=\frac{(x-2)(x-3)}{(x-3)(x+3)}=\frac{x-2}{x+3},\qquad x\ne3$$
So,
$$-1\le\frac{x-2}{x+3}\le1$$
First solve
$$\frac{x-2}{x+3}\ge-1$$
$$\frac{x-2+x+3}{x+3}\ge0$$
$$\frac{2x+1}{x+3}\ge0$$
Hence,
$$x\in(-\infty,-3)\cup\left[-\frac12,\infty\right)$$
Now solve
$$\frac{x-2}{x+3}\le1$$
$$\frac{x-2-x-3}{x+3}\le0$$
$$\frac{-5}{x+3}\le0$$
$$x>-3$$
Combining both,
$$x\in\left[-\frac12,\infty\right)$$
Now,
$$x^2-3x+2=(x-1)(x-2)$$
For logarithm to exist,
$$(x-1)(x-2)>0$$
$$x<1\quad\text{or}\quad x>2$$
Also,
$$\log(x^2-3x+2)\ne0$$
$$x^2-3x+2\ne1$$
$$x^2-3x+1\ne0$$
This condition is automatically satisfied in the final interval.
Also,
$$x\ne3$$
Therefore, combining all conditions,
$$x\in\left[-\frac12,1\right)\cup(2,\infty)-\{3\}$$
Hence, the correct answer is
$$\boxed{\left[-\frac12,1\right)\cup(2,\infty)-\{3\}}$$
Let $$y = y_1(x)$$ and $$y = y_2(x)$$ be two distinct solutions of the differential equation $$\frac{dy}{dx} = x + y$$, with $$y_1(0) = 0$$ and $$y_2(0) = 1$$ respectively. Then, the number of points of intersection of $$y = y_1(x)$$ and $$y = y_2(x)$$ is
We need to find the negation of $$(p \wedge q) \rightarrow (q \vee r)$$.
Step 1: Recall the negation of implication
The negation of $$P \rightarrow Q$$ is $$P \wedge (\sim Q)$$.
Here, $$P = p \wedge q$$ and $$Q = q \vee r$$.
Step 2: Apply the negation
$$\sim[(p \wedge q) \rightarrow (q \vee r)] = (p \wedge q) \wedge \sim(q \vee r)$$
Step 3: Simplify $$\sim(q \vee r)$$
By De Morgan's law: $$\sim(q \vee r) = (\sim q) \wedge (\sim r)$$
Step 4: Combine
$$(p \wedge q) \wedge (\sim q) \wedge (\sim r) = p \wedge q \wedge (\sim q) \wedge (\sim r)$$
Hence, the correct answer is Option A: $$p \wedge q \wedge (\sim q) \wedge (\sim r)$$.
The maximum number of compound propositions, out of $$p \vee r \vee s$$, $$p \vee r \vee \sim s$$, $$p \vee \sim q \vee s$$, $$\sim p \vee \sim r \vee s$$, $$\sim p \vee \sim r \vee \sim s$$, $$\sim p \vee q \vee \sim s$$, $$q \vee r \vee \sim s$$, $$q \vee \sim r \vee \sim s$$, $$\sim p \vee \sim q \vee \sim s$$ that can be made simultaneously true by an assignment of the truth values to $$p, q, r$$ and $$s$$, is equal to
We need to find the maximum number of the 9 given compound propositions that can be made simultaneously true by assigning truth values to $$p, q, r, s$$.
The 9 propositions are:
1. $$p \vee r \vee s$$ 2. $$p \vee r \vee \sim s$$ 3. $$p \vee \sim q \vee s$$
4. $$\sim p \vee \sim r \vee s$$ 5. $$\sim p \vee \sim r \vee \sim s$$ 6. $$\sim p \vee q \vee \sim s$$
7. $$q \vee r \vee \sim s$$ 8. $$q \vee \sim r \vee \sim s$$ 9. $$\sim p \vee \sim q \vee \sim s$$
Strategy:
There are $$2^4 = 16$$ possible truth value assignments for $$(p, q, r, s)$$. A disjunction (OR) is false only when all its operands are false. We systematically check assignments to maximize the count of true propositions.
Try $$p = T,\; q = T,\; r = F,\; s = F$$:
Evaluate each proposition:
1. $$T \vee F \vee F = T$$ $$\checkmark$$
2. $$T \vee F \vee T = T$$ $$\checkmark$$
3. $$T \vee F \vee F = T$$ $$\checkmark$$
4. $$F \vee T \vee F = T$$ $$\checkmark$$
5. $$F \vee T \vee T = T$$ $$\checkmark$$
6. $$F \vee T \vee T = T$$ $$\checkmark$$
7. $$T \vee F \vee T = T$$ $$\checkmark$$
8. $$T \vee T \vee T = T$$ $$\checkmark$$
9. $$F \vee F \vee T = T$$ $$\checkmark$$
All 9 propositions are true.
Verify this is indeed the maximum:
Since all 9 propositions are satisfied by the assignment $$(p, q, r, s) = (T, T, F, F)$$, the maximum possible number is 9.
The answer is $$\boxed{9}$$.
The number of functions $$f$$, from the set $$A = \{x \in \mathbb{N}: x^2 - 10x + 9 \leq 0\}$$ to the set $$B = \{n^2 : n \in \mathbb{N}\}$$ such that $$f(x) \leq (x-3)^2 + 1$$, for every $$x \in A$$, is _______.
We need to find the number of functions $$f: A \to B$$ such that $$f(x)\le (x-3)^2 + 1$$ for every $$x\in A$$.
From the inequality $$x^2 - 10x + 9 \le 0$$ we have $$(x-1)(x-9)\le 0$$, which implies $$1\le x\le 9$$. Since $$x\in\mathbb{N}$$, it follows that $$A = \{1,2,3,4,5,6,7,8,9\}$$.
Also, by definition, $$B = \{n^2 : n\in\mathbb{N}\} = \{1,4,9,16,25,36,\ldots\}$$.
For each $$x$$ we require $$f(x)\le (x-3)^2 + 1$$ and $$f(x)\in B$$. We list the bounds and counts:
When $$x=1$$, $$(x-3)^2 + 1 = 4 + 1 = 5$$, so the eligible values in $$B$$ are $$\{1,4\}$$, giving 2 choices.
When $$x=2$$, $$(x-3)^2 + 1 = 1 + 1 = 2$$, so the eligible values in $$B$$ are $$\{1\}$$, giving 1 choice.
When $$x=3$$, $$(x-3)^2 + 1 = 0 + 1 = 1$$, so the eligible values in $$B$$ are $$\{1\}$$, giving 1 choice.
When $$x=4$$, $$(x-3)^2 + 1 = 1 + 1 = 2$$, so the eligible values in $$B$$ are $$\{1\}$$, giving 1 choice.
When $$x=5$$, $$(x-3)^2 + 1 = 4 + 1 = 5$$, so the eligible values in $$B$$ are $$\{1,4\}$$, giving 2 choices.
When $$x=6$$, $$(x-3)^2 + 1 = 9 + 1 = 10$$, so the eligible values in $$B$$ are $$\{1,4,9\}$$, giving 3 choices.
When $$x=7$$, $$(x-3)^2 + 1 = 16 + 1 = 17$$, so the eligible values in $$B$$ are $$\{1,4,9,16\}$$, giving 4 choices.
When $$x=8$$, $$(x-3)^2 + 1 = 25 + 1 = 26$$, so the eligible values in $$B$$ are $$\{1,4,9,16,25\}$$, giving 5 choices.
When $$x=9$$, $$(x-3)^2 + 1 = 36 + 1 = 37$$, so the eligible values in $$B$$ are $$\{1,4,9,16,25,36\}$$, giving 6 choices.
Since the choices at each $$x$$ are independent, the total number of such functions is
$$2 \times 1 \times 1 \times 1 \times 2 \times 3 \times 4 \times 5 \times 6 = 1440$$.
The answer is $$\boxed{1440}$$.
Let $$S = \{1, 2, 3, 4, 5, 6, 7, 8, 9, 10\}$$. Define $$f : S \to S$$ as $$f(n) = \begin{cases} 2n, & \text{if } n = 1,2,3,4,5 \\ 2n-11 & \text{if } n = 6,7,8,9,10 \end{cases}$$
Let $$g : S \geq S$$ be a function such that $$fog(n) = \begin{cases} n+1, & \text{if } n \text{ is odd} \\ n-1, & \text{if } n \text{ is even} \end{cases}$$, then
$$g(10)(g(1) + g(2) + g(3) + g(4) + g(5))$$ is equal to ______
Given $$S = \{1, 2, \ldots, 10\}$$ and $$f: S \to S$$ defined by:
$$f(n) = \begin{cases} 2n & \text{if } n = 1,2,3,4,5 \\ 2n - 11 & \text{if } n = 6,7,8,9,10 \end{cases}$$
So: $$f(1)=2,\; f(2)=4,\; f(3)=6,\; f(4)=8,\; f(5)=10,\; f(6)=1,\; f(7)=3,\; f(8)=5,\; f(9)=7,\; f(10)=9$$
Note that $$f$$ is a bijection. Its inverse is:
$$f^{-1}(k) = \begin{cases} k/2 & \text{if } k \text{ is even} \\ (k+11)/2 & \text{if } k \text{ is odd} \end{cases}$$
We need $$g: S \to S$$ such that $$f \circ g(n) = \begin{cases} n+1 & \text{if } n \text{ is odd} \\ n-1 & \text{if } n \text{ is even} \end{cases}$$
Since $$f$$ is bijective: $$g(n) = f^{-1}(f \circ g(n))$$.
Computing each value:
$$g(1) = f^{-1}(2) = 1, \quad g(2) = f^{-1}(1) = 6, \quad g(3) = f^{-1}(4) = 2$$
$$g(4) = f^{-1}(3) = 7, \quad g(5) = f^{-1}(6) = 3$$
$$g(6) = f^{-1}(5) = 8, \quad g(7) = f^{-1}(8) = 4, \quad g(8) = f^{-1}(7) = 9$$
$$g(9) = f^{-1}(10) = 5, \quad g(10) = f^{-1}(9) = 10$$
Now compute:
$$g(1) + g(2) + g(3) + g(4) + g(5) = 1 + 6 + 2 + 7 + 3 = 19$$
$$g(10) = 10$$
$$g(10) \cdot (g(1) + g(2) + g(3) + g(4) + g(5)) = 10 \times 19 = 190$$
The correct answer is $$\boxed{190}$$.
Let $$f:\mathbb{R}\to\mathbb{R}$$ be a function defined by $$f(x)=\left(2\left(1-\frac{x^{25}}{2}\right)(2+x^{25})\right)^{\frac{1}{50}}.$$ If the function $$g(x)=f(f(f(x)))+f(f(x)),$$ then the greatest integer less than or equal to $$g(1)$$ is ____________.
Given,
$$f(x)=\left(2\left(1-\frac{x^{25}}{2}\right)(2+x^{25})\right)^{\frac{1}{50}}$$
Simplifying,
$$f(x)=\left((2-x^{25})(2+x^{25})\right)^{\frac{1}{50}}$$
$$f(x)=\left(4-x^{50}\right)^{\frac{1}{50}}$$
Now,
$$f(f(x))=\left(4-\left((4-x^{50})^{\frac{1}{50}}\right)^{50}\right)^{\frac{1}{50}}$$
$$=\left(4-(4-x^{50})\right)^{\frac{1}{50}}$$
$$=(x^{50})^{\frac{1}{50}}=x$$
Hence,
$$f(f(x))=x$$
Given,
$$g(x)=f(f(f(x)))+f(f(x))$$
Using $$f(f(x))=x,$$
$$g(x)=f(x)+x$$
Now,
$$f(1)=\left(4-1^{50}\right)^{\frac{1}{50}}=3^{\frac{1}{50}}$$
Therefore,
$$g(1)=3^{\frac{1}{50}}+1$$
Since,
$$1<3^{\frac{1}{50}}<2$$
we get,
$$2<g(1)<3$$
Therefore, the greatest integer less than or equal to $$g(1)$$ is $$\boxed{2}$$.
Let $$S = \{1, 2, 3, 4\}$$. Then the number of elements in the set $$\{f : S \times S \to S : f$$ is onto and $$f(a,b) = f(b,a) \geq a \forall (a,b) \in S \times S\}$$ is
We need to count functions $$f : S \times S \to S$$ (where $$S = \{1,2,3,4\}$$) that are onto, symmetric ($$f(a,b) = f(b,a)$$), and satisfy $$f(a,b) \geq a$$ for all $$(a,b) \in S \times S$$.
Analyzing the constraint $$f(a,b) \geq a$$, since $$f(a,b) = f(b,a)$$, we also need $$f(a,b) \geq b$$. Therefore:
$$f(a,b) \geq \max(a,b)$$
Next, because $$f(a,b) \in S = \{1,2,3,4\}$$ and $$f(a,b) \geq \max(a,b)$$, we have $$f(4,b) \geq 4$$ for all $$b$$, so $$f(4,b) = 4$$. Similarly, $$f(a,4) = 4$$. This fixes all values involving 4.
Now consider values involving only $$\{1,2,3\}$$. For $$(a,b)$$ with $$a,b \in \{1,2,3\}$$, we have $$f(a,b) \geq \max(a,b)$$. Since $$f$$ is symmetric, we only need to specify $$f(a,b)$$ for $$a \leq b$$.
$$f(3,3) \geq 3$$: choices are $$\{3,4\}$$ (2 choices)
$$f(2,3) = f(3,2) \geq 3$$: choices are $$\{3,4\}$$ (2 choices)
$$f(1,3) = f(3,1) \geq 3$$: choices are $$\{3,4\}$$ (2 choices)
$$f(2,2) \geq 2$$: choices are $$\{2,3,4\}$$ (3 choices)
$$f(1,2) = f(2,1) \geq 2$$: choices are $$\{2,3,4\}$$ (3 choices)
$$f(1,1) \geq 1$$: choices are $$\{1,2,3,4\}$$ (4 choices)
Without the onto constraint, the total number of assignments is $$2 \times 2 \times 2 \times 3 \times 3 \times 4 = 288$$.
The value 4 is already achieved from the forced values. We need the values 1, 2, and 3 to each appear at least once.
Value 1 can only appear at $$f(1,1)$$, so $$f(1,1) = 1$$ is forced. This reduces choices for $$f(1,1)$$ to 1 option.
Value 2 can appear at $$f(1,2)$$ or $$f(2,2)$$, and it must appear in at least one of those entries.
Value 3 can appear at $$f(3,3)$$, $$f(2,3)$$, $$f(1,3)$$, $$f(2,2)$$, or $$f(1,2)$$.
With $$f(1,1) = 1$$, the remaining free choices are:
$$f(3,3)$$: $$\{3,4\}$$, $$f(2,3)$$: $$\{3,4\}$$, $$f(1,3)$$: $$\{3,4\}$$, $$f(2,2)$$: $$\{2,3,4\}$$, $$f(1,2)$$: $$\{2,3,4\}$$.
Without the onto requirement for 2 and 3, there are $$2 \times 2 \times 2 \times 3 \times 3 = 72$$ assignments.
To ensure both 2 and 3 appear, we use inclusion-exclusion. Let $$A$$ be the set of assignments where 2 does not appear, and $$B$$ the set where 3 does not appear.
In $$A$$, we must have $$f(1,2) \in \{3,4\}$$ and $$f(2,2) \in \{3,4\}$$, giving $$|A| = 2 \times 2 \times 2 \times 2 \times 2 = 32$$.
In $$B$$, we must have $$f(3,3) = f(2,3) = f(1,3) = 4$$ and $$f(2,2), f(1,2) \in \{2,4\}$$, giving $$|B| = 1 \times 1 \times 1 \times 2 \times 2 = 4$$.
In $$A \cap B$$, both 2 and 3 are absent, so all five free values must be 4, giving $$|A \cap B| = 1$$.
By inclusion-exclusion, the number of valid assignments is $$72 - 32 - 4 + 1 = 37$$.
The answer is $$\boxed{37}$$.
The negation of the statement $$\sim p \wedge (p \vee q)$$ is:
We need to find the negation of $$\sim p \wedge (p \vee q)$$.
Applying De Morgan's law, the negation is $$\sim(\sim p) \vee \sim(p \vee q)$$, which simplifies to $$p \vee (\sim p \wedge \sim q)$$.
Now we apply the distributive law: $$p \vee (\sim p \wedge \sim q) = (p \vee \sim p) \wedge (p \vee \sim q)$$.
Since $$p \vee \sim p$$ is always true (a tautology), this reduces to $$T \wedge (p \vee \sim q) = p \vee \sim q$$.
Therefore, the negation of $$\sim p \wedge (p \vee q)$$ is $$p \vee \sim q$$.
For the statements $$p$$ and $$q$$, consider the following compound statements:
$$(a)$$ $$(\sim q \wedge (p \to q)) \to \sim p$$
$$(b)$$ $$((p \vee q) \wedge \sim p) \to q$$
Then which of the following statements is correct?
We need to determine whether statements (a) $$(\sim q \wedge (p \to q)) \to \sim p$$ and (b) $$((p \vee q) \wedge \sim p) \to q$$ are tautologies.
For statement (a), recall that $$p \to q \equiv \sim p \vee q$$. So $$\sim q \wedge (p \to q) = \sim q \wedge (\sim p \vee q) = (\sim q \wedge \sim p) \vee (\sim q \wedge q) = \sim p \wedge \sim q$$, since $$\sim q \wedge q$$ is always false. The statement becomes $$(\sim p \wedge \sim q) \to \sim p$$. Since the hypothesis $$\sim p \wedge \sim q$$ contains $$\sim p$$, the implication is always true. So (a) is a tautology.
For statement (b), we simplify $$(p \vee q) \wedge \sim p = (\sim p \wedge p) \vee (\sim p \wedge q) = F \vee (\sim p \wedge q) = \sim p \wedge q$$. The statement becomes $$(\sim p \wedge q) \to q$$. Since the hypothesis contains $$q$$, the implication is always true. So (b) is also a tautology.
Therefore, both (a) and (b) are tautologies.
Consider the following three statements:
(A) If $$3 + 3 = 7$$ then $$4 + 3 = 8$$
(B) If $$5 + 3 = 8$$ then earth is flat.
(C) If both (A) and (B) are true then $$5 + 6 = 17$$.
Then, which of the following statements is correct?
We evaluate the truth value of each statement using the rule that a conditional $$p \Rightarrow q$$ is false only when $$p$$ is true and $$q$$ is false.
Statement (A): "If $$3 + 3 = 7$$ then $$4 + 3 = 8$$." The hypothesis $$3 + 3 = 7$$ is false. A conditional with a false hypothesis is vacuously true. So (A) is true.
Statement (B): "If $$5 + 3 = 8$$ then the earth is flat." Here $$5 + 3 = 8$$ is true, but "the earth is flat" is false. A conditional with a true hypothesis and false conclusion is false. So (B) is false.
Statement (C): "If both (A) and (B) are true then $$5 + 6 = 17$$." Since (B) is false, the hypothesis "(A) and (B) are true" is false. Therefore (C) is vacuously true. So (C) is true.
Thus (A) and (C) are true while (B) is false.
The Boolean expression $$(p \wedge q) \Rightarrow ((r \wedge q) \wedge p)$$ is equivalent to:
We have to simplify the statement $$ (p \wedge q)\;\Rightarrow\;\bigl((r \wedge q)\;\wedge\;p\bigr)\;. $$
First recall the basic implication law:
$$A \Rightarrow B \;\equiv\; \neg A \,\vee\, B.$$
Before using the law, it is convenient to tidy up the right-hand conjunction. Because conjunction is both commutative and associative, we may rearrange the factors freely:
$$ (r \wedge q) \wedge p \;=\; p \wedge q \wedge r. $$
So the whole expression becomes
$$ (p \wedge q)\;\Rightarrow\;(p \wedge q \wedge r). $$
Now set $$A = (p \wedge q),\qquad B = (p \wedge q \wedge r).$$ Applying the implication law we obtain
$$ \neg(p \wedge q) \;\vee\; (p \wedge q \wedge r). $$
Next, use De Morgan’s rule for the negation of a conjunction:
$$ \neg(p \wedge q) \;=\; \neg p \;\vee\; \neg q. $$
Substituting this result we have
$$ (\neg p \;\vee\; \neg q) \;\vee\; (p \wedge q \wedge r). $$
The disjunction symbol “∨” is associative, so we can write the whole thing as
$$ \neg p \;\vee\; \neg q \;\vee\; (p \wedge q \wedge r). $$
To see the final simplification clearly, break the analysis into the two possible truth-values of $$q$$.
Case 1: $$q$$ is false. If $$q$$ is false, then $$\neg q$$ is true, and the entire disjunction is automatically true. Therefore the expression is true irrespective of $$p$$ and $$r$$.
Case 2: $$q$$ is true. If $$q$$ is true, the term $$\neg q$$ becomes false, and the disjunction reduces to
$$ \neg p \;\vee\; (p \wedge r). $$
Factor $$p$$ out of the second term:
$$ \neg p \;\vee\; \bigl(p \wedge r\bigr) \;=\; (\neg p \;\vee\; p) \wedge (\neg p \;\vee\; r) \;=\; \text{T} \wedge (\neg p \;\vee\; r) \;=\; \neg p \;\vee\; r. $$
Hence, when $$q$$ is true, the original statement is equivalent to $$\neg p \;\vee\; r$$. Remembering that $$q$$ itself is true in this case, $$\neg p \;\vee\; r \quad\equiv\quad \neg p \;\vee\; (r \wedge q).$$ (The factor $$q$$ can be inserted because $$q$$ is already true and $$r \wedge q$$ therefore has the same truth value as $$r$$.)
Combining both cases, we can write the simplified form valid for all truth-values of $$p,q,r$$ as
$$ \neg p \;\vee\; \neg q \;\vee\; (r \wedge q). $$
Finally recognise this again as an implication, with antecedent $$(p \wedge q)$$ and consequent $$(r \wedge q)$$:
$$ \neg(p \wedge q) \;\vee\; (r \wedge q) \;\equiv\; (p \wedge q) \Rightarrow (r \wedge q). $$
Thus the original Boolean expression is logically equivalent to $$ (p \wedge q) \Rightarrow (r \wedge q). $$
Comparing with the given options, this matches Option C.
Hence, the correct answer is Option C.
The Boolean expression $$(p \wedge \sim q) \Rightarrow (q \vee \sim p)$$ is equivalent to:
We need to simplify $$(p \wedge \sim q) \Rightarrow (q \vee \sim p)$$.
Using the equivalence $$A \Rightarrow B \equiv \sim A \vee B$$, we write: $$\sim(p \wedge \sim q) \vee (q \vee \sim p).$$
By De Morgan's law, $$\sim(p \wedge \sim q) = \sim p \vee q$$. Substituting: $$(\sim p \vee q) \vee (q \vee \sim p) = \sim p \vee q.$$
The expression $$\sim p \vee q$$ is precisely the conditional $$p \Rightarrow q$$.
Therefore $$(p \wedge \sim q) \Rightarrow (q \vee \sim p)$$ is equivalent to $$p \Rightarrow q$$.
Let $$F_1(A, B, C) = (A \wedge \sim B) \vee [\sim C \wedge (A \vee B)] \vee \sim A$$ and $$F_2(A, B) = (A \vee B) \vee (B \to \sim A)$$ be two logical expressions. Then:
We are given $$F_1(A, B, C) = (A \wedge \sim B) \vee [\sim C \wedge (A \vee B)] \vee \sim A$$ and $$F_2(A, B) = (A \vee B) \vee (B \to \sim A)$$.
First, we check whether $$F_1$$ is a tautology. Consider $$A = T$$, $$B = T$$, $$C = T$$: $$(T \wedge F) \vee [F \wedge (T \vee T)] \vee F = F \vee F \vee F = F$$. Since $$F_1$$ evaluates to $$F$$ for this assignment, $$F_1$$ is not a tautology.
Next, we check $$F_2$$. Recall that $$B \to \sim A \equiv \sim B \vee \sim A$$. So $$F_2 = (A \vee B) \vee (\sim B \vee \sim A) = (A \vee \sim A) \vee (B \vee \sim B) = T \vee T = T$$.
More explicitly, rearranging: $$F_2 = A \vee B \vee \sim B \vee \sim A = (A \vee \sim A) \vee (B \vee \sim B) = T$$. So $$F_2$$ is always true, making it a tautology.
Therefore $$F_1$$ is not a tautology but $$F_2$$ is a tautology.
The Boolean expression $$(p \Rightarrow q) \wedge (q \Rightarrow \sim p)$$ is equivalent to:
We have to simplify the Boolean expression $$ (p \Rightarrow q)\;\wedge\; (q \Rightarrow \sim p)\,. $$
First, recall the standard logical equivalence for an implication. The implication formula states:
$$ a \Rightarrow b \;\equiv\; \sim a \,\vee\, b. $$
Applying this to each implication in our expression, we replace the arrows by disjunctions:
For the first part, $$p \Rightarrow q \equiv \sim p \vee q.$$
For the second part, $$q \Rightarrow \sim p \equiv \sim q \vee \sim p.$$
Substituting these two results back into the original conjunction, we obtain
$$ (\sim p \vee q)\;\wedge\;(\sim q \vee \sim p). $$
Now we notice that both disjunctions contain the common literal $$\sim p.$$ To combine the two clauses, we use the distributive law of Boolean algebra, which says
$$ (A \vee B)\;\wedge\;(A \vee C)\;=\;A \;\vee\;(B \wedge C). $$
Here, we match the symbols as follows:
$$A = \sim p,\quad B = q,\quad C = \sim q.$$
Substituting into the distributive formula, we get
$$ (\sim p \vee q)\;\wedge\;(\sim p \vee \sim q)\;=\;\sim p\;\vee\;(q \wedge \sim q). $$
The expression $$q \wedge \sim q$$ is always false, because a statement and its negation can never be true at the same time. Hence
$$ q \wedge \sim q = \text{False}. $$
Therefore, our entire expression simplifies to
$$ \sim p \;\vee\; \text{False} \;=\; \sim p. $$
So the Boolean expression $$ (p \Rightarrow q) \wedge (q \Rightarrow \sim p) $$ is logically equivalent to $$\sim p.$$
Looking at the given options, $$\sim p$$ appears as Option D.
Hence, the correct answer is Option D.
The contrapositive of the statement "If you will work, you will earn money" is:
The given statement is of the form "If $$P$$, then $$Q$$", where $$P$$ = "you will work" and $$Q$$ = "you will earn money".
The contrapositive of "If $$P$$, then $$Q$$" is "If not $$Q$$, then not $$P$$".
Substituting, the contrapositive is: "If you will not earn money, you will not work".
The statement among the following that is a tautology is:
We need to identify which statement is a tautology (always true regardless of truth values of $$A$$ and $$B$$).
Option D is $$(A \wedge (A \to B)) \to B$$. This is the well-known rule of Modus Ponens.
Let us verify using a truth table. When $$A$$ is True and $$B$$ is True: $$A \to B$$ is True, so $$A \wedge (A \to B)$$ is True, and $$\text{True} \to \text{True}$$ is True.
When $$A$$ is True and $$B$$ is False: $$A \to B$$ is False, so $$A \wedge (A \to B)$$ is False, and $$\text{False} \to \text{False}$$ is True.
When $$A$$ is False and $$B$$ is True: $$A \to B$$ is True, so $$A \wedge (A \to B)$$ is False, and $$\text{False} \to \text{True}$$ is True.
When $$A$$ is False and $$B$$ is False: $$A \to B$$ is True, so $$A \wedge (A \to B)$$ is False, and $$\text{False} \to \text{False}$$ is True.
In all cases the result is True, confirming this is a tautology.
Hence, the correct answer is Option D.
Which of the following Boolean expressions is not a tautology?
We need to identify which Boolean expression is NOT a tautology. Recall that $$p \Rightarrow q \equiv \sim p \vee q$$.
Option A: $$(p \Rightarrow q) \vee (\sim q \Rightarrow p) \equiv (\sim p \vee q) \vee (q \vee p) \equiv (\sim p \vee p) \vee q \equiv T \vee q \equiv T$$. This is a tautology.
Option B: $$(q \Rightarrow p) \vee (\sim q \Rightarrow p) \equiv (\sim q \vee p) \vee (q \vee p) \equiv (\sim q \vee q) \vee p \equiv T \vee p \equiv T$$. This is a tautology.
Option C: $$(p \Rightarrow \sim q) \vee (\sim q \Rightarrow p) \equiv (\sim p \vee \sim q) \vee (q \vee p) \equiv (\sim p \vee p) \vee (\sim q \vee q) \equiv T \vee T \equiv T$$. This is a tautology.
Option D: $$(\sim p \Rightarrow q) \vee (\sim q \Rightarrow p) \equiv (p \vee q) \vee (q \vee p) \equiv p \vee q$$. When $$p = F$$ and $$q = F$$, this equals $$F$$. So this is NOT a tautology.
The answer is Option D.
If $$P$$ and $$Q$$ are two statements, then which of the following compound statement is a tautology?
We need to check which compound statement is a tautology. Option 2 is $$((P \Rightarrow Q) \wedge \sim Q) \Rightarrow \sim P$$. This is precisely the law of Modus Tollens, a well-known logical tautology: if $$P$$ implies $$Q$$ and $$Q$$ is false, then $$P$$ must be false.
To verify, suppose the antecedent $$(P \Rightarrow Q) \wedge \sim Q$$ is true. Then $$\sim Q$$ is true, so $$Q$$ is false. Since $$P \Rightarrow Q$$ is also true and $$Q$$ is false, $$P$$ must be false (if $$P$$ were true, $$P \Rightarrow Q$$ would be false). Hence $$\sim P$$ is true, and the implication holds. If the antecedent is false, the implication is vacuously true. Therefore the statement is always true, confirming it is a tautology.
Let $$*, \square \in \{\wedge, \vee\}$$ be such that the Boolean expression $$(p * \sim q) \Rightarrow (p \square q)$$ is a tautology. Then:
We have to select the two connectives $$*$$ and $$\square$$ from the set $$\{\wedge ,\vee\}$$ in such a way that the statement
$$ (\,p * \sim q\,)\;\Rightarrow\;(p \;\square\; q) $$
is a tautology, that is, it must be true for every possible truth-value assignment of the propositional variables $$p$$ and $$q$$.
First recall the standard equivalence that rewrites an implication:
$$ a \Rightarrow b \;\equiv\; \lnot a \;\vee\; b. $$
Applying this formula to our expression we obtain
$$ (\,p * \sim q\,)\;\Rightarrow\;(p \square q) \;\equiv\; \lnot\,(p * \sim q) \;\vee\; (p \square q). $$
Because $$*$$ and $$\square$$ may each be either $$\wedge$$ (AND) or $$\vee$$ (OR), four distinct combinations are possible. We test them one by one, showing every algebraic step.
Case 1: $$*=\wedge,\;\square=\vee$$
Substituting these symbols gives
$$ \lnot\,(p \wedge \sim q) \;\vee\; (p \vee q). $$
We now push the negation inside the parenthesis with De Morgan’s law:
$$ \lnot (p \wedge \sim q) \;\equiv\; (\lnot p) \;\vee\; (\lnot\!\sim q) \;=\; (\lnot p) \;\vee\; q. $$
Therefore the whole expression becomes
$$ \big((\lnot p) \;\vee\; q\big) \;\vee\; (p \;\vee\; q). $$
Using associativity and commutativity of $$\vee$$ we group the disjuncts that involve $$p$$:
$$ \big((\lnot p) \;\vee\; p\big) \;\vee\; q. $$
Since a proposition OR its negation is always true, we have
$$ (\lnot p) \;\vee\; p \;=\; \text{T} \quad\text{(a tautology).} $$
Thus the entire expression simplifies to
$$ \text{T} \;\vee\; q \;=\; \text{T}. $$
So for $$*=\wedge,\;\square=\vee$$ the implication is always true; hence this choice makes the given statement a tautology.
Case 2: $$*=\wedge,\;\square=\wedge$$
The expression now is
$$ \lnot\,(p \wedge \sim q) \;\vee\; (p \wedge q) \;=\; (\lnot p \;\vee\; q) \;\vee\; (p \wedge q). $$
To check whether this is a tautology, take the assignment $$p=\text{T},\;q=\text{F}$$ (i.e. $$p=1,q=0$$).
Then we get
$$ \lnot p = 0,\quad q = 0,\quad p \wedge q = 1\wedge 0 = 0. $$
So the whole disjunction becomes $$0\;\vee\;0=0$$, which is false. Hence this case fails to be a tautology.
Case 3: $$*=\vee,\;\square=\vee$$
We have
$$ \lnot\,(p \vee \sim q) \;\vee\; (p \vee q). $$
Again by De Morgan,
$$ \lnot\,(p \vee \sim q) \;=\; (\lnot p) \wedge q. $$
Hence the whole statement is
$$ \big((\lnot p) \wedge q\big) \;\vee\; (p \vee q). $$
Choose $$p=\text{F},\;q=\text{F}$$. Then
$$ (\lnot p)\wedge q = 1\wedge 0 = 0,\quad p\vee q = 0\vee 0 = 0, $$
so the overall value is $$0\vee 0 = 0$$—not a tautology.
Case 4: $$*=\vee,\;\square=\wedge$$
The expression becomes
$$ \lnot\,(p \vee \sim q) \;\vee\; (p \wedge q) \;=\; ((\lnot p) \wedge q) \;\vee\; (p \wedge q). $$
With the assignment $$p=\text{F},\;q=\text{F}$$ we get
$$ (\lnot p)\wedge q = 1\wedge 0 = 0,\quad p\wedge q = 0\wedge 0 = 0, $$
so the disjunction is again $$0\vee 0 = 0$$. Hence this case also fails to be a tautology.
Among all four possibilities, only Case 1—namely $$*=\wedge$$ and $$\square=\vee$$—produces a statement that is true under every possible truth assignment. All other choices admit at least one counter-example, so they are not tautologies.
Hence, the correct answer is Option C.
Negation of the statement $$(p \vee r) \Rightarrow (q \vee r)$$ is:
We begin with the given statement of implication
$$ (p \vee r) \Rightarrow (q \vee r). $$
First, we recall the logical equivalence that an implication $$A \Rightarrow B$$ can be rewritten as $$\sim A \,\vee\, B.$$ Stating this clearly:
$$ A \Rightarrow B \;\; \text{is equivalent to} \;\; \sim A \vee B. $$
Here, the role of $$A$$ is played by $$(p \vee r)$$ and the role of $$B$$ is played by $$(q \vee r).$$ Applying the formula gives
$$ (p \vee r) \Rightarrow (q \vee r) \;\; \equiv \;\; \sim(p \vee r) \,\vee\, (q \vee r). $$
Now we want the negation of the entire implication. So we place a negation sign in front of the whole expression we just obtained:
$$ \sim\!\bigl[(p \vee r) \Rightarrow (q \vee r)\bigr] \;=\; \sim\!\bigl[\;\sim(p \vee r) \,\vee\, (q \vee r)\bigr]. $$
Next, we use De Morgan’s law, which states that the negation of a disjunction is the conjunction of the negations:
$$ \sim(A \vee B) \;\equiv\; \sim A \,\wedge\, \sim B. $$
Applying this law with $$A = \sim(p \vee r)$$ and $$B = (q \vee r),$$ we get
$$ \sim\!\bigl[\;\sim(p \vee r) \,\vee\, (q \vee r)\bigr] \;=\; \bigl[\;\sim\!\bigl(\sim(p \vee r)\bigr)\bigr] \,\wedge\, \bigl[\;\sim(q \vee r)\bigr]. $$
Simplify each part separately. First, note that the double negation law tells us $$\sim(\sim X) = X.$$ Therefore,
$$ \sim\!\bigl(\,\sim(p \vee r)\bigr) \;=\; (p \vee r). $$
For the second part, we again apply De Morgan’s law:
$$ \sim(q \vee r) \;=\; (\sim q) \,\wedge\, (\sim r). $$
Substituting these simplified pieces back, the negation becomes
$$ (p \vee r) \,\wedge\, \bigl[(\sim q) \wedge (\sim r)\bigr]. $$
Associativity of $$\wedge$$ allows us to drop parentheses inside the conjunction, giving
$$ (p \vee r) \,\wedge\, \sim q \,\wedge\, \sim r. $$
Now we must distribute $$(p \vee r)$$ over the other conjunctive factors. Using the distributive property $$ (X \vee Y)\,\wedge\,Z \;\equiv\; (X \wedge Z) \vee (Y \wedge Z), $$ with $$X = p,\; Y = r,\; Z = (\sim q \wedge \sim r),$$ we have
$$ (p \vee r) \,\wedge\, \sim q \,\wedge\, \sim r \;=\; \bigl[p \wedge (\sim q) \wedge (\sim r)\bigr] \;\vee\; \bigl[r \wedge (\sim q) \wedge (\sim r)\bigr]. $$
Observe that the second term contains the factor $$(r \wedge \sim r),$$ which is always false. Hence that entire term vanishes, leaving only
$$ p \,\wedge\, \sim q \,\wedge\, \sim r. $$
Thus, the negation of $$(p \vee r) \Rightarrow (q \vee r)$$ simplifies completely to
$$ p \wedge \sim q \wedge \sim r. $$
Comparing with the options provided, this matches Option C.
Hence, the correct answer is Option C.
Which of the following Boolean expression is a tautology?
First recall some basic logical equivalences that we will use repeatedly.
$$p \rightarrow q$$ is equivalent to $$\neg p \vee q$$ $$-(1)$$
De Morgan’s laws: $$\neg(p \wedge q)=\neg p \vee \neg q$$ and $$\neg(p \vee q)=\neg p \wedge \neg q$$.
We will analyse every option one by one and see whether the statement is always true (tautology) or not.
Case A:
Expression: $$ (p \wedge q) \vee (p \vee q) $$
The term $$p \vee q$$ already contains every situation covered by $$p \wedge q$$, so using the absorption law
$$ (p \wedge q) \vee (p \vee q)=p \vee q $$.
$$p \vee q$$ is not always true (for $$p=\text{False},\,q=\text{False}$$ it is False).
Hence Option A is NOT a tautology.
Case B:
Expression: $$ (p \wedge q) \vee (p \rightarrow q) $$
Using $$-(1)$$, rewrite:
$$ (p \wedge q) \vee (\neg p \vee q) $$.
Group the disjunctions:
$$ =(\neg p \vee q) \vee (p \wedge q) $$.
Construct a truth-table for the three literals $$\neg p,\,q,\,p \wedge q$$ (or test the four combinations of $$p,q$$):
• $$p=\text{T},\,q=\text{T}$$: expression T
• $$p=\text{T},\,q=\text{F}$$: $$\neg p \vee q=\text{F},\,p\wedge q=\text{F}$$ ⇒ overall F
As it becomes False, the statement is not a tautology. Hence Option B is NOT a tautology.
Case C:
Expression: $$ (p \wedge q) \wedge (p \rightarrow q) $$
Again substitute $$p \rightarrow q=\neg p \vee q$$:
$$ (p \wedge q) \wedge (\neg p \vee q) $$.
If $$p=\text{F},\;q=\text{T}$$ then the first part $$p \wedge q=\text{F}$$, so whole expression is False. Therefore it is NOT a tautology.
Case D:
Expression: $$ (p \wedge q) \rightarrow (p \rightarrow q) $$
First convert the implication using $$-(1)$$:
$$ (p \wedge q) \rightarrow (p \rightarrow q)=\neg(p \wedge q) \vee (p \rightarrow q) $$
Apply De Morgan’s law on the first term and $$-(1)$$ on the second term:
$$ =(\neg p \vee \neg q) \vee (\neg p \vee q) $$
Associativity and commutativity of $$\vee$$ let us group the literals:
$$ =\neg p \vee \neg q \vee q $$
But $$\neg q \vee q$$ is always True, so
$$\neg p \vee (\neg q \vee q)=\neg p \vee \text{True}=\text{True}$$
Since the expression reduces to True for every choice of $$p$$ and $$q$$, it is a tautology.
Therefore, only Option D $$\big((p \wedge q) \rightarrow (p \rightarrow q)\big)$$ is a tautology.
Final Answer: Option D.
Which of the following is equivalent to the Boolean expression $$p \wedge \sim q$$?
We have to find an option whose logical value is always identical to the expression $$p \wedge \sim q$$. The expression $$p \wedge \sim q$$ is true exactly when $$p$$ is true and $$q$$ is false, and false in every other situation. We shall translate each option into a form that can be compared directly with this conjunction.
First, we recall and state the fundamental implication law: for any statements $$x$$ and $$y$$,
$$x \rightarrow y \;\equiv\; \sim x \;\vee\; y.$$
Using this single law and ordinary De Morgan simplifications $$\sim(x \vee y)=\sim x \wedge \sim y$$ and $$\sim(x \wedge y)=\sim x \vee \sim y,$$ we convert every option step by step.
Option A is $$\sim p \rightarrow \sim q$$. Applying the implication law with $$x=\sim p$$ and $$y=\sim q$$ gives
$$\sim p \rightarrow \sim q \;\equiv\; \sim(\sim p) \;\vee\; \sim q.$$
Now $$\sim(\sim p)=p$$, so
$$\sim p \rightarrow \sim q \;\equiv\; p \;\vee\; \sim q.$$
Thus Option A simplifies to $$p \vee \sim q$$, a disjunction, not the required conjunction $$p \wedge \sim q$$. Hence Option A is not equivalent.
Option B is $$\sim\bigl(q \rightarrow p\bigr)$$. First write the inner implication:
$$q \rightarrow p \;\equiv\; \sim q \;\vee\; p.$$
Substituting, we get
$$\sim\bigl(q \rightarrow p\bigr) \;=\; \sim\bigl(\sim q \;\vee\; p\bigr).$$
Using De Morgan’s law for negation of a disjunction,
$$\sim(\sim q \;\vee\; p) \;=\; \sim(\sim q) \;\wedge\; \sim p.$$
Now $$\sim(\sim q)=q,$$ so
$$\sim\bigl(q \rightarrow p\bigr) \;\equiv\; q \;\wedge\; \sim p.$$
This is the conjunction $$q \wedge \sim p,$$ which is different from $$p \wedge \sim q$$. Therefore Option B is also not equivalent.
Option C is $$\sim\bigl(p \rightarrow q\bigr).$$ Again we expand the implication:
$$p \rightarrow q \;\equiv\; \sim p \;\vee\; q.$$
Substituting gives
$$\sim\bigl(p \rightarrow q\bigr) \;=\; \sim\bigl(\sim p \;\vee\; q\bigr).$$
Using De Morgan’s law,
$$\sim(\sim p \;\vee\; q) \;=\; \sim(\sim p) \;\wedge\; \sim q.$$
Simplifying $$\sim(\sim p)=p,$$ we obtain
$$\sim\bigl(p \rightarrow q\bigr) \;\equiv\; p \;\wedge\; \sim q.$$
This is exactly the original expression we wanted. So Option C matches $$p \wedge \sim q$$ perfectly.
Option D is $$\sim\bigl(p \rightarrow \sim q\bigr).$$ Start with the implication:
$$p \rightarrow \sim q \;\equiv\; \sim p \;\vee\; \sim q.$$
Negating it,
$$\sim\bigl(p \rightarrow \sim q\bigr) \;=\; \sim\bigl(\sim p \;\vee\; \sim q\bigr).$$
Applying De Morgan’s law,
$$\sim(\sim p \;\vee\; \sim q) \;=\; \sim(\sim p) \;\wedge\; \sim(\sim q).$$
This simplifies to
$$p \;\wedge\; q.$$
Since $$p \wedge q$$ differs from $$p \wedge \sim q,$$ Option D is not equivalent.
Among all four options, only Option C reduces to $$p \wedge \sim q$$. Hence, the correct answer is Option 3.
If the Boolean expression $$(p \Rightarrow q) \Leftrightarrow (q * (\sim p))$$ is a tautology, then the Boolean expression $$p * (\sim q)$$ is equivalent to:
We are given that $$(p \Rightarrow q) \Leftrightarrow (q * (\sim p))$$ is a tautology, and we need to find what $$p * (\sim q)$$ is equivalent to.
Recall the standard logical equivalence: $$p \Rightarrow q \equiv \sim p \lor q$$. This means "if p then q" is the same as "not-p or q".
For the biconditional $$(p \Rightarrow q) \Leftrightarrow (q * (\sim p))$$ to be a tautology, both sides must always have the same truth value. So we need $$\sim p \lor q \equiv q * (\sim p)$$ for every combination of truth values of $$p$$ and $$q$$.
Let us substitute $$a = \sim p$$ to simplify. Then we need $$a \lor q \equiv q * a$$ for all truth values of $$a$$ and $$q$$. Since $$a$$ and $$q$$ range over all truth values independently (as $$p$$ and $$q$$ do), this means the operation $$*$$ must be exactly the same as $$\lor$$ (OR).
To verify with a truth table: when $$a = T, q = T$$: $$a \lor q = T$$ so $$q * a = T$$. When $$a = T, q = F$$: $$a \lor q = T$$ so $$q * a = T$$. When $$a = F, q = T$$: $$a \lor q = T$$ so $$q * a = T$$. When $$a = F, q = F$$: $$a \lor q = F$$ so $$q * a = F$$. This matches the OR truth table exactly.
Now we evaluate $$p * (\sim q)$$. Since $$*$$ is $$\lor$$, we get $$p * (\sim q) = p \lor (\sim q)$$.
Using the equivalence $$q \Rightarrow p \equiv \sim q \lor p = p \lor (\sim q)$$, we see that $$p * (\sim q) \equiv q \Rightarrow p$$.
This matches Option A: $$q \Rightarrow p$$.
Let $$A = \{1, 2, 3, \ldots, 10\}$$ and $$f : A \to A$$ be defined as
$$f(k) = \begin{cases} k + 1 & \text{if } k \text{ is odd} \\ k & \text{if } k \text{ is even} \end{cases}$$
Then the number of possible functions $$g : A \to A$$ such that $$gof = f$$ is:
The function $$f : A \to A$$ is defined as $$f(k) = k + 1$$ if $$k$$ is odd, and $$f(k) = k$$ if $$k$$ is even. So: $$f(1) = 2$$, $$f(2) = 2$$, $$f(3) = 4$$, $$f(4) = 4$$, $$f(5) = 6$$, $$f(6) = 6$$, $$f(7) = 8$$, $$f(8) = 8$$, $$f(9) = 10$$, $$f(10) = 10$$.
The range of $$f$$ is $$\{2, 4, 6, 8, 10\}$$. We need $$g \circ f = f$$, i.e., $$g(f(k)) = f(k)$$ for all $$k \in A$$.
This means $$g(2) = 2$$, $$g(4) = 4$$, $$g(6) = 6$$, $$g(8) = 8$$, and $$g(10) = 10$$. These five values of $$g$$ are completely determined.
However, the values $$g(1)$$, $$g(3)$$, $$g(5)$$, $$g(7)$$, and $$g(9)$$ are not constrained by the condition $$g \circ f = f$$ (since 1, 3, 5, 7, 9 are not in the range of $$f$$). Each of these can be any element of $$A = \{1, 2, \ldots, 10\}$$.
Therefore the number of possible functions $$g$$ is $$10 \times 10 \times 10 \times 10 \times 10 = 10^5$$.
The statement $$(p \wedge (p \rightarrow q) \wedge (q \rightarrow r)) \rightarrow r$$ is
We have to inspect the compound statement $$\bigl(p \wedge (p \rightarrow q) \wedge (q \rightarrow r)\bigr) \rightarrow r$$ and decide whether it is always true (a tautology), always false (a fallacy), or equivalent to some simpler implication.
First of all, recall the standard equivalence for an implication:
$$x \rightarrow y \;\;\text{is logically equal to}\;\; \sim x \vee y.$$
Using this rule, we rewrite each implication inside the larger expression.
$$p \rightarrow q \equiv \sim p \vee q,$$
$$q \rightarrow r \equiv \sim q \vee r.$$
Substituting these into the original statement gives
$$\Bigl(p \wedge (\sim p \vee q) \wedge (\sim q \vee r)\Bigr) \rightarrow r.$$
Let us now simplify the conjunction in the antecedent, step by step.
First combine the first two factors:
$$p \wedge (\sim p \vee q) = (p \wedge \sim p) \vee (p \wedge q).$$
But $$p \wedge \sim p$$ is a contradiction, hence equal to false. So
$$(p \wedge \sim p) \vee (p \wedge q) = \text{false} \vee (p \wedge q) = p \wedge q.$$
Thus the antecedent has now become
$$(p \wedge q) \wedge (\sim q \vee r).$$
We keep going. Group the last two factors:
$$q \wedge (\sim q \vee r) = (q \wedge \sim q) \vee (q \wedge r).$$
Again $$q \wedge \sim q$$ is a contradiction, so this reduces to
$$(q \wedge \sim q) \vee (q \wedge r) = \text{false} \vee (q \wedge r) = q \wedge r.$$
Hence the whole antecedent simplifies neatly to
$$p \wedge (q \wedge r) = p \wedge q \wedge r.$$
The complete statement is therefore
$$(p \wedge q \wedge r) \rightarrow r.$$
Apply the implication equivalence once more:
$$(p \wedge q \wedge r) \rightarrow r \equiv \sim(p \wedge q \wedge r) \vee r.$$
By De Morgan’s law,
$$\sim(p \wedge q \wedge r) = \sim p \vee \sim q \vee \sim r.$$
So the entire disjunction becomes
$$\bigl(\sim p \vee \sim q \vee \sim r\bigr) \vee r.$$
Now observe that $$\sim r \vee r$$ is a tautology (it is always true). Because that tautology is one of the disjuncts, the whole expression is invariably true, no matter what truth-values $$p, q,$$ and $$r$$ may take.
Therefore the original statement is always true; that is, it is a tautology.
Hence, the correct answer is Option A.
If the Boolean expression $$(p \wedge q) \circledast (p \otimes q)$$ is a tautology, then $$\circledast$$ and $$\otimes$$ are respectively given by:
We need to find the connectives $$\circledast$$ and $$\otimes$$ such that $$(p \wedge q) \circledast (p \otimes q)$$ is a tautology.
Let us check Option A: $$\circledast$$ is $$\to$$ and $$\otimes$$ is $$\to$$. The expression becomes $$(p \wedge q) \to (p \to q)$$.
Recall that an implication $$A \to B$$ is false only when $$A$$ is true and $$B$$ is false. So $$(p \wedge q) \to (p \to q)$$ is false only when $$(p \wedge q)$$ is true and $$(p \to q)$$ is false.
If $$(p \wedge q)$$ is true, then both $$p$$ and $$q$$ are true. But when $$p$$ is true and $$q$$ is true, $$(p \to q)$$ is also true. So the antecedent being true forces the consequent to be true as well.
Therefore $$(p \wedge q) \to (p \to q)$$ can never be false, making it a tautology.
Let us verify the other options fail. For Option B ($$\circledast = \wedge$$, $$\otimes = \vee$$): the expression is $$(p \wedge q) \wedge (p \vee q)$$. When $$p = T, q = F$$: $$(T \wedge F) \wedge (T \vee F) = F \wedge T = F$$. Not a tautology.
For Option C ($$\circledast = \vee$$, $$\otimes = \to$$): the expression is $$(p \wedge q) \vee (p \to q)$$. When $$p = T, q = F$$: $$(T \wedge F) \vee (T \to F) = F \vee F = F$$. Not a tautology.
For Option D ($$\circledast = \wedge$$, $$\otimes = \to$$): the expression is $$(p \wedge q) \wedge (p \to q)$$. When $$p = F, q = F$$: $$(F \wedge F) \wedge (F \to F) = F \wedge T = F$$. Not a tautology.
The answer is $$\to, \to$$, which is Option A.
Let $$f: R \to R$$ be defined as $$f(x) = 2x - 1$$ and $$g: R - \{1\} \to R$$. be defined as $$g(x) = \frac{x - \frac{1}{2}}{x - 1}$$. Then the composition function $$f(g(x))$$ is:
We have $$f(x) = 2x - 1$$ and $$g(x) = \frac{x - \frac{1}{2}}{x - 1}$$, with domain of $$g$$ being $$\mathbb{R} - \{1\}$$.
The composition is $$f(g(x)) = 2 \cdot \frac{x - \frac{1}{2}}{x - 1} - 1 = \frac{2x - 1}{x - 1} - 1 = \frac{2x - 1 - (x - 1)}{x - 1} = \frac{x}{x - 1}$$.
The domain of $$f(g(x))$$ is $$\mathbb{R} - \{1\}$$.
To check one-one: suppose $$\frac{x_1}{x_1 - 1} = \frac{x_2}{x_2 - 1}$$. Then $$x_1(x_2 - 1) = x_2(x_1 - 1)$$, giving $$x_1 x_2 - x_1 = x_1 x_2 - x_2$$, so $$x_1 = x_2$$. The function is one-one.
To check onto: let $$\frac{x}{x - 1} = y$$. Then $$x = y(x - 1) = yx - y$$, so $$x(1 - y) = -y$$, giving $$x = \frac{y}{y - 1}$$. This requires $$y \neq 1$$. So the range is $$\mathbb{R} - \{1\}$$, which is not all of $$\mathbb{R}$$.
Therefore $$f(g(x))$$ is one-one but not onto.
Hence, the correct answer is Option B.
Let $$f(x) = \sin^{-1}x$$ and $$g(x) = \frac{x^2 - x - 2}{2x^2 - x - 6}$$. If $$g(2) = \lim_{x \to 2} g(x)$$, then the domain of the function $$fog$$ is
We have $$g(x) = \dfrac{x^2 - x - 2}{2x^2 - x - 6} = \dfrac{(x-2)(x+1)}{(2x+3)(x-2)}$$. For $$x \neq 2$$, this simplifies to $$g(x) = \dfrac{x + 1}{2x + 3}$$.
Since $$g(2) = \displaystyle\lim_{x \to 2} g(x) = \dfrac{3}{7}$$, the function $$g$$ is defined as $$g(x) = \dfrac{x+1}{2x+3}$$ for all $$x \neq -\dfrac{3}{2}$$.
For $$f \circ g$$ to be defined, we need $$-1 \leq g(x) \leq 1$$ (the domain of $$\sin^{-1}$$).
Condition 1: $$g(x) \geq -1$$, i.e., $$\dfrac{x+1}{2x+3} \geq -1$$. This gives $$\dfrac{x + 1 + 2x + 3}{2x+3} = \dfrac{3x + 4}{2x + 3} \geq 0$$. By sign analysis, this holds when $$x \leq -\dfrac{3}{2}$$ or $$x \geq -\dfrac{4}{3}$$.
Condition 2: $$g(x) \leq 1$$, i.e., $$\dfrac{x+1}{2x+3} \leq 1$$. This gives $$\dfrac{x + 1 - 2x - 3}{2x + 3} = \dfrac{-(x+2)}{2x+3} \leq 0$$, equivalently $$\dfrac{x + 2}{2x + 3} \geq 0$$. By sign analysis, this holds when $$x \leq -2$$ or $$x > -\dfrac{3}{2}$$.
Taking the intersection (and excluding $$x = -\dfrac{3}{2}$$ where $$g$$ is undefined): $$\left(x \leq -\dfrac{3}{2} \text{ or } x \geq -\dfrac{4}{3}\right) \cap \left(x \leq -2 \text{ or } x > -\dfrac{3}{2}\right) = (-\infty, -2] \cup \left[-\dfrac{4}{3}, \infty\right)$$.
Therefore the domain of $$f \circ g$$ is $$\left(-\infty, -2\right] \cup \left[-\dfrac{4}{3}, \infty\right)$$.
Let $$g : N \to N$$ be defined as
$$g(3n+1) = 3n+2$$
$$g(3n+2) = 3n+3$$
$$g(3n+3) = 3n+1$$, for all $$n \ge 0$$
Then which of the following statements is true?
We begin by rewriting the definition of the given function in the language of congruence-classes because this will make every later step completely transparent. For any natural number $$x\in \mathbb N$$ we can write $$x=3n+1,\;3n+2$$ or $$3n+3$$ for a unique $$n\ge 0$$. Using this unique representation we have
$$ g(3n+1)=3n+2,\qquad g(3n+2)=3n+3,\qquad g(3n+3)=3n+1,\qquad n\ge 0. $$So, whenever $$x\equiv 1\pmod 3$$ or $$x\equiv 2\pmod 3$$, the value of $$g$$ is simply $$x+1$$, while for $$x\equiv 0\pmod 3$$ the value becomes $$x-2$$. Placing the three cases side by side we see that every set
$$ \{\,3n+1,\;3n+2,\;3n+3\,\} $$forms a closed cycle under $$g$$:
$$ 3n+1\;\xrightarrow{g}\;3n+2\;\xrightarrow{g}\;3n+3\;\xrightarrow{g}\;3n+1. $$Because the cycle length is exactly three, applying $$g$$ three times brings us back to the starting point:
$$ g(g(g(x))) = x\qquad\text{for every }x\in\mathbb N. $$In compact notation this is written as $$g^3 = \operatorname{id}_{\mathbb N}$$. Therefore $$g^3$$ is the identity, while $$g$$ itself is not the identity (no natural number is fixed). We will now test each option one after another.
Testing Option A. We must find a surjective (onto) function $$f:\mathbb N\to\mathbb N$$ satisfying
$$ f\bigl(g(x)\bigr)=f(x)\quad\text{for all }x\in\mathbb N. $$Let us first analyse the algebraic condition. Substituting the three possible forms of $$x$$ we get
$$ \begin{aligned} x=3n+1 &\;\Longrightarrow\; f\bigl(g(3n+1)\bigr)=f(3n+1) \\[2pt] &\;\Longrightarrow\; f(3n+2)=f(3n+1),\\[6pt] x=3n+2 &\;\Longrightarrow\; f\bigl(g(3n+2)\bigr)=f(3n+2) \\[2pt] &\;\Longrightarrow\; f(3n+3)=f(3n+2),\\[6pt] x=3n+3 &\;\Longrightarrow\; f\bigl(g(3n+3)\bigr)=f(3n+3) \\[2pt] &\;\Longrightarrow\; f(3n+1)=f(3n+3). \end{aligned} $$Combining the three equalities we obtain the single rule
$$ f(3n+1)=f(3n+2)=f(3n+3)\quad\text{for every }n\ge 0. $$In words, each entire 3-cycle must be sent to one and the same value. But we are still free to choose which value that is, for every individual cycle. A very convenient (and classical) choice is
$$ f(3n+1)=f(3n+2)=f(3n+3)=n+1,\qquad n\ge 0. $$Now we check surjectivity. Given any natural number $$k\in\mathbb N$$, set $$n=k-1$$ (allowed because $$k\ge 1$$). Then $$f(3n+1)=k$$, so $$k$$ lies in the image. Thus the function hits every natural number, i.e. it is onto. Because the function also satisfies the required equality, Option A is true.
Testing Option B. The same algebraic argument used above tells us that any $$f$$ with $$f\circ g=f$$ must be constant on each 3-cycle. Hence there will always be at least three distinct inputs having the same output, immediately contradicting the definition of a one-one (injective) function. Therefore Option B is false.
Testing Option C. We have already observed that $$g^3=\operatorname{id}_{\mathbb N}$$, so
$$ g\circ g\circ g = \operatorname{id}_{\mathbb N}\neq g, $$because no element is fixed by $$g$$. Hence $$gogog=g$$ is incorrect, making Option C false.
Testing Option D. Here we seek an $$f$$ such that $$g\circ f=f$$. Writing this out we have
$$ g\bigl(f(x)\bigr)=f(x)\quad\text{for all }x\in\mathbb N. $$This means every value taken by $$f$$ must be a fixed point of $$g$$. Yet we saw earlier that $$g$$ possesses no fixed point at all. Consequently no such $$f$$ can exist, and Option D is also false.
Only Option A survives every check. Hence, the correct answer is Option A.
Let $$[x]$$ denote the greatest integer less than or equal to $$x$$. Then, the values of $$x \in R$$ satisfying the equation $$[e^x]^2 + [e^x + 1] - 3 = 0$$ lie in the interval:
We need to solve $$[e^x]^2 + [e^x + 1] - 3 = 0$$, where $$[y]$$ is the greatest integer (floor) function.
Using the property $$[y + n] = [y] + n$$ for any integer $$n$$: $$[e^x + 1] = [e^x] + 1$$.
The equation becomes $$[e^x]^2 + [e^x] + 1 - 3 = 0$$, i.e., $$[e^x]^2 + [e^x] - 2 = 0$$.
Let $$t = [e^x]$$. Then $$t^2 + t - 2 = 0$$, so $$(t+2)(t-1) = 0$$, giving $$t = 1$$ or $$t = -2$$.
Since $$e^x > 0$$ for all real $$x$$, we have $$[e^x] \geq 0$$, so $$t = -2$$ is rejected.
Thus $$[e^x] = 1$$, meaning $$1 \leq e^x < 2$$.
Taking natural logarithm: $$0 \leq x < \log_e 2$$.
The values of $$x$$ lie in $$[0, \log_e 2)$$, which is Option D.
The statement $$A \to (B \to A)$$ is equivalent to:
We need to determine which statement is logically equivalent to $$A \to (B \to A)$$.
First, we simplify $$A \to (B \to A)$$. Since $$B \to A \equiv \neg B \vee A$$, we have $$A \to (B \to A) \equiv \neg A \vee (\neg B \vee A) \equiv (\neg A \vee A) \vee \neg B \equiv \text{True}$$.
So $$A \to (B \to A)$$ is a tautology (always true regardless of the truth values of $$A$$ and $$B$$).
Now we check the options. For $$A \to (A \vee B)$$: this equals $$\neg A \vee (A \vee B) \equiv (\neg A \vee A) \vee B \equiv \text{True}$$. This is also a tautology.
Since both $$A \to (B \to A)$$ and $$A \to (A \vee B)$$ are tautologies, they are logically equivalent (both are always true).
Therefore, $$A \to (B \to A)$$ is equivalent to $$A \to (A \vee B)$$.
If the domain of the function $$f(x) = \frac{\cos^{-1}\sqrt{x^2 - x + 1}}{\sqrt{\sin^{-1}\left(\frac{2x-1}{2}\right)}}$$ is the interval $$(\alpha, \beta]$$, then $$\alpha + \beta$$ is equal to:
We need to find the domain of $$f(x) = \frac{\cos^{-1}\sqrt{x^2 - x + 1}}{\sqrt{\sin^{-1}\left(\frac{2x-1}{2}\right)}}$$.
Condition 1 (square root inside cos inverse): We need $$x^2 - x + 1 \geq 0$$. The discriminant is $$1 - 4 = -3 < 0$$ with positive leading coefficient, so this is always positive. Always satisfied.
Condition 2 (argument of cos inverse in $$[-1,1]$$): Since $$\sqrt{x^2 - x + 1} \geq 0$$, we need $$\sqrt{x^2 - x + 1} \leq 1$$, i.e., $$x^2 - x + 1 \leq 1$$, so $$x^2 - x \leq 0$$, giving $$x(x-1) \leq 0$$, i.e., $$0 \leq x \leq 1$$.
Condition 3 (argument of sin inverse in $$[-1,1]$$): $$-1 \leq \frac{2x-1}{2} \leq 1$$ gives $$-\frac{1}{2} \leq x \leq \frac{3}{2}$$.
Condition 4 (denominator positive): $$\sin^{-1}\left(\frac{2x-1}{2}\right) > 0$$. Since $$\sin^{-1}(t) > 0$$ iff $$t > 0$$, we need $$\frac{2x-1}{2} > 0$$, i.e., $$x > \frac{1}{2}$$.
Intersecting all conditions: $$0 \leq x \leq 1$$ and $$x > \frac{1}{2}$$ gives $$\frac{1}{2} < x \leq 1$$, i.e., the interval $$\left(\frac{1}{2}, 1\right]$$.
So $$\alpha = \frac{1}{2}$$ and $$\beta = 1$$, giving $$\alpha + \beta = \frac{3}{2}$$.
The answer is $$\frac{3}{2}$$, which is Option A.
Let $$f : N \rightarrow N$$ be a function such that $$f(m+n) = f(m) + f(n)$$ for every $$m, n \in N$$. If $$f(6) = 18$$ then $$f(2) \cdot f(3)$$ is equal to:
We are given a function $$f : \mathbb N \rightarrow \mathbb N$$ satisfying the additive property
$$f(m+n)=f(m)+f(n) \quad \text{for all } m,n\in\mathbb N.$$
First, we recall the standard fact that if a function on the natural numbers is additive in this way, then its value at any positive integer can be built up by repeatedly adding the value at $$1$$. More precisely, we use the principle of mathematical induction:
For $$n=1$$ the statement $$f(1)=f(1)$$ is trivially true. Now assume $$f(k)=k\,f(1)$$ for some $$k\in\mathbb N$$. Then, using the given property,
$$f(k+1)=f(k)+f(1).$$
Substituting the induction hypothesis $$f(k)=k\,f(1)$$, we obtain
$$f(k+1)=k\,f(1)+f(1)=(k+1)\,f(1).$$
Thus by induction the general formula
$$f(n)=n\,f(1) \quad\text{holds for every } n\in\mathbb N.$$
Now we use the given numerical information. We are told that
$$f(6)=18.$$
Applying the formula $$f(6)=6\,f(1)$$ we write
$$6\,f(1)=18.$$
Dividing both sides by $$6$$, we get
$$f(1)=\frac{18}{6}=3.$$
With $$f(1)$$ known, we can find the required values:
For $$n=2$$,
$$f(2)=2\,f(1)=2\times 3=6.$$
For $$n=3$$,
$$f(3)=3\,f(1)=3\times 3=9.$$
The question asks for the product $$f(2)\cdot f(3)$$. Substituting the values just found,
$$f(2)\cdot f(3)=6\times 9=54.$$
Hence, the correct answer is Option A.
Let $$f : R - \{\frac{\alpha}{6}\} \to R$$ be defined by $$f(x) = \left(\frac{5x+3}{6x-\alpha}\right)$$. Then the value of $$\alpha$$ for which $$(f \circ f)(x) = x$$, for all $$x \in R - \{\frac{\alpha}{6}\}$$, is:
We have $$f(x) = \frac{5x + 3}{6x - \alpha}$$. We need $$(f \circ f)(x) = x$$ for all $$x \in R \setminus \{\frac{\alpha}{6}\}$$.
Computing $$f(f(x))$$ directly: let $$u = f(x) = \frac{5x+3}{6x-\alpha}$$, then $$f(u) = \frac{5u + 3}{6u - \alpha} = \frac{5\cdot\frac{5x+3}{6x-\alpha} + 3}{6\cdot\frac{5x+3}{6x-\alpha} - \alpha}.$$
Multiplying numerator and denominator by $$(6x - \alpha)$$: $$f(f(x)) = \frac{5(5x+3) + 3(6x-\alpha)}{6(5x+3) - \alpha(6x-\alpha)} = \frac{25x + 15 + 18x - 3\alpha}{30x + 18 - 6\alpha x + \alpha^2}.$$
For this to equal $$x$$ for all valid $$x$$, we need $$\frac{(25+18)x + (15-3\alpha)}{(30-6\alpha)x + (18+\alpha^2)} = x$$, i.e., $$(43)x + (15-3\alpha) = x\left[(30-6\alpha)x + (18+\alpha^2)\right].$$
For this to hold as an identity, the coefficient of $$x^2$$ on the right must be zero: $$30 - 6\alpha = 0$$, but this gives $$\alpha = 5$$. Let us verify: with $$\alpha = 5$$, the numerator becomes $$(25+18)x + (15-15) = 43x$$ and the denominator becomes $$(30-30)x + (18+25) = 43$$, so $$f(f(x)) = \frac{43x}{43} = x$$. ✓
Therefore $$\alpha = 5$$.
Let $$[x]$$ denote the greatest integer $$\le x$$, where $$x \in R$$. If the domain of the real valued function $$f(x) = \sqrt{\frac{|x|-2}{|x|-3}}$$ is $$(-\infty, a) \cup [b, c) \cup [4, \infty)$$, $$a < b < c$$, then the value of $$a + b + c$$ is:
The problem defines $$[x]$$ as the greatest integer function. The function under consideration is $$f(x) = \sqrt{\dfrac{|[x]|-2}{|[x]|-3}}$$, which requires $$\dfrac{|[x]|-2}{|[x]|-3} \ge 0$$ with $$|[x]| \ne 3$$.
Setting $$n = [x]$$ (an integer), the condition $$\dfrac{|n|-2}{|n|-3} \ge 0$$ holds when $$|n| \le 2$$ or $$|n| \ge 4$$ (excluding $$|n| = 3$$).
We translate each integer condition back to $$x$$, using $$[x] = n \iff x \in [n, n+1)$$.
For $$|n| \le 2$$: $$n \in \{-2,-1,0,1,2\}$$, so $$x \in [-2,-1) \cup [-1,0) \cup [0,1) \cup [1,2) \cup [2,3) = [-2, 3)$$.
For $$|n| = 3$$ (excluded): $$n = -3$$ gives $$x \in [-3,-2)$$, and $$n = 3$$ gives $$x \in [3,4)$$. These are excluded from the domain.
For $$|n| \ge 4$$: $$n \le -4$$ gives $$x \in (-\infty,-3)$$, and $$n \ge 4$$ gives $$x \in [4,\infty)$$.
Therefore the domain is $$(-\infty,-3) \cup [-2,3) \cup [4,\infty)$$.
Matching with the given form $$(-\infty, a) \cup [b,c) \cup [4,\infty)$$: we identify $$a = -3$$, $$b = -2$$, $$c = 3$$.
Hence $$a + b + c = -3 + (-2) + 3 = -2$$.
Let $$f, g : N \to N$$ such that $$f(n + 1) = f(n) + f(1)$$ $$\forall n \in N$$ and $$g$$ be any arbitrary function. Which of the following statements is NOT true?
Given $$f(n + 1) = f(n) + f(1)$$ for all $$n \in \mathbb{N}$$, we can deduce that $$f(n) = n \cdot f(1)$$ for all $$n \in \mathbb{N}$$ (by induction). Let $$f(1) = k$$ where $$k \in \mathbb{N}$$, so $$f(n) = kn$$.
Checking Option A: If $$f$$ is onto, then every natural number must be in the range. Since $$f(n) = kn$$, the range is $$\{k, 2k, 3k, \ldots\}$$. For this to equal $$\mathbb{N}$$, we need $$k = 1$$, so $$f(n) = n$$. This statement is TRUE.
Checking Option C: $$f$$ is one-one. Since $$f(n) = kn$$ and $$k \geq 1$$, if $$f(m) = f(n)$$ then $$km = kn$$ so $$m = n$$. This statement is TRUE.
Checking Option D: If $$f \circ g$$ is one-one, then $$g$$ is one-one. If $$g(m) = g(n)$$, then $$f(g(m)) = f(g(n))$$, and since $$f \circ g$$ is one-one, we must have $$m = n$$. This statement is TRUE.
Checking Option B: If $$g$$ is onto, then $$f \circ g$$ is one-one. Consider the counterexample where $$k = 1$$ (so $$f(n) = n$$) and define $$g$$ as: $$g(1) = g(2) = 1$$ and $$g(n) = n - 1$$ for $$n \geq 3$$. Then $$g$$ is onto (every natural number is in the range), but $$f(g(1)) = f(1) = 1 = f(1) = f(g(2))$$ while $$1 \neq 2$$, so $$f \circ g$$ is NOT one-one. This statement is NOT TRUE.
Therefore, the statement that is NOT true is: if $$g$$ is onto, then $$f \circ g$$ is one-one.
If $$[x]$$ be the greatest integer less than or equal to $$x$$, then $$\sum_{n=8}^{100} \left[\frac{(-1)^n n}{2}\right]$$ is equal to:
We have to evaluate the finite sum
$$\sum_{n=8}^{100}\left[\frac{(-1)^n\,n}{2}\right]$$
where $$[x]$$ denotes the greatest integer less than or equal to $$x$$ (the “floor” of $$x$$).
First we separate the index $$n$$ into the two possible parities because the factor $$(-1)^n$$ behaves differently for even and odd indices.
For an even integer $$n$$ we can write $$n=2k$$. Then $$(-1)^n = 1$$, so
$$\frac{(-1)^n\,n}{2}= \frac{1\cdot 2k}{2}=k,$$ and since $$k$$ is already an integer, its greatest-integer value is
$$\left[\frac{(-1)^n\,n}{2}\right]=k=\frac{n}{2}.$$
For an odd integer $$n$$ we can write $$n=2k+1$$. Then $$(-1)^n = -1$$, so
$$\frac{(-1)^n\,n}{2}= \frac{-1\cdot(2k+1)}{2}= -\left(k+\tfrac12\right).$$
The number $$-\!\left(k+\tfrac12\right)$$ lies strictly between the two consecutive integers $$-(k+1)$$ and $$-k$$ and is less than both of them, hence its greatest-integer value is
$$\left[\frac{(-1)^n\,n}{2}\right]=-(k+1)= -\frac{n+1}{2}.$$
So, term by term,
$$ \left[\frac{(-1)^n\,n}{2}\right]= \begin{cases} \dfrac{n}{2}, & n \text{ even},\\[6pt] -\dfrac{n+1}{2}, & n \text{ odd}. \end{cases} $$
Now we split the required sum into its even and odd parts:
$$ \sum_{n=8}^{100}\Bigl[\tfrac{(-1)^n n}{2}\Bigr] =\sum_{\substack{n=8\\ n\text{ even}}}^{100}\frac{n}{2} +\sum_{\substack{n=8\\ n\text{ odd}}}^{100}\!\!\!\!\left(-\frac{n+1}{2}\right). $$
The even values of $$n$$ run from 8 to 100: 8, 10, 12, …, 100.
There are
$$\frac{100-8}{2}+1=\frac{92}{2}+1=46+1=47$$
such even integers. For each of them we take half, giving the consecutive integers
$$4,\,5,\,6,\ldots,\,50$$
(because $$8/2=4$$ and $$100/2=50$$). Their sum is obtained by the formula for an arithmetic progression:
$$ \sum_{\text{even }n}\frac{n}{2} =\frac{\text{number of terms}}{2}\,( \text{first term}+\text{last term}) =\frac{47}{2}\,(4+50) =\frac{47}{2}\times54 =47\times27 =1269. $$
The odd values of $$n$$ run from 9 to 99:
9, 11, 13, …, 99.
There are 46 of them, because the total count 93 minus the 47 evens gives 46 odds. For each odd $$n$$ we substitute $$-\dfrac{n+1}{2}$$. Now $$(n+1)/2$$ for these odds is the consecutive list
$$5,\,6,\,7,\ldots,\,50,$$
and taking the negative gives
$$-5,\,-6,\,-7,\ldots,\,-50.$$
Again using the arithmetic-progression formula, the sum of these 46 integers is
$$ \sum_{\text{odd }n}\left(-\frac{n+1}{2}\right) =-\,\frac{46}{2}\,(5+50) =-\,23\times55 =-1265. $$
Combining the even and odd contributions:
$$ \sum_{n=8}^{100}\Bigl[\tfrac{(-1)^n n}{2}\Bigr] =1269 + (-1265)=4. $$
Hence, the correct answer is Option B.
Let $$f : R - \{3\} \to R - \{1\}$$ be defined by $$f(x) = \frac{x-2}{x-3}$$. Let $$g : R \to R$$ be given as $$g(x) = 2x - 3$$. Then, the sum of all the values of $$x$$ for which $$f^{-1}(x) + g^{-1}(x) = \frac{13}{2}$$ is equal to
Given $$f(x) = \frac{x-2}{x-3}$$, we find $$f^{-1}$$. Setting $$y = \frac{x-2}{x-3}$$, we solve for $$x$$: $$y(x-3) = x - 2$$, so $$yx - 3y = x - 2$$, giving $$x(y-1) = 3y - 2$$, hence $$x = \frac{3y - 2}{y - 1}$$. Therefore $$f^{-1}(x) = \frac{3x - 2}{x - 1}$$.
Given $$g(x) = 2x - 3$$, we find $$g^{-1}(x) = \frac{x + 3}{2}$$.
The equation $$f^{-1}(x) + g^{-1}(x) = \frac{13}{2}$$ becomes $$\frac{3x-2}{x-1} + \frac{x+3}{2} = \frac{13}{2}$$. Multiplying through by $$2(x-1)$$: $$2(3x-2) + (x+3)(x-1) = 13(x-1)$$. Expanding: $$6x - 4 + x^2 + 2x - 3 = 13x - 13$$. This simplifies to $$x^2 + 8x - 7 = 13x - 13$$, so $$x^2 - 5x + 6 = 0$$, which factors as $$(x-2)(x-3) = 0$$.
Thus $$x = 2$$ or $$x = 3$$. Both values are in the domain of $$f^{-1}$$ (since $$x \neq 1$$). The sum of all values is $$2 + 3 = 5$$.
Consider function $$f : A \rightarrow B$$ and $$g : B \rightarrow C$$ $$(A, B, C \subseteq R)$$ such that $$(gof)^{-1}$$ exists, then:
We begin with the information that $$f:A\rightarrow B$$ and $$g:B\rightarrow C$$ are two real-valued functions such that the composite function $$g\circ f:A\rightarrow C$$ possesses an inverse, written $$(g\circ f)^{-1}$$.
A function admits an inverse if and only if it is bijective; that is, it must be simultaneously one-one (injective) and onto (surjective). Hence we may immediately state
$$g\circ f \text{ is one-one and onto.}$$
We now translate the bijectivity of $$g\circ f$$ into separate conditions on $$f$$ and $$g$$.
Injectivity part: To prove that $$f$$ is one-one, let us take any two elements $$x_{1},x_{2}\in A$$ and assume that their images under $$f$$ coincide, i.e.
$$f(x_{1})=f(x_{2}).$$
Applying $$g$$ on both sides we obtain
$$g\!\left(f(x_{1})\right)=g\!\left(f(x_{2})\right) \;\Longrightarrow\; (g\circ f)(x_{1})=(g\circ f)(x_{2}).$$
Since $$g\circ f$$ is injective, equality of the outputs forces equality of the inputs, so
$$x_{1}=x_{2}.$$
This derivation shows that no two distinct elements of $$A$$ can share the same image under $$f$$; therefore $$f$$ is one-one (injective).
Surjectivity part: To show that $$g$$ is onto, start with an arbitrary element $$c\in C$$. Because $$g\circ f$$ is surjective, there exists some $$a\in A$$ satisfying
$$(g\circ f)(a)=c.$$
Writing the composition explicitly, this reads
$$g\!\bigl(f(a)\bigr)=c.$$
Denote $$b=f(a)\in B$$; then the equation becomes $$g(b)=c$$. We have thus produced an element $$b\in B$$ whose image under $$g$$ is the pre-selected $$c$$, verifying that every element of $$C$$ is attained by $$g$$. Consequently, $$g$$ is onto (surjective).
Putting the two deductions together, we have established that
$$f \text{ is one-one and } g \text{ is onto.}$$
None of the other combinations is compelled by the mere bijectivity of $$g\circ f$$. Hence, the correct answer is Option C.
The inverse of $$y = 5^{\log x}$$ is:
We need the inverse function of $$y = 5^{\log x}$$.
Taking logarithm (base 10) on both sides: $$\log y = \log x \cdot \log 5$$.
Solving for $$\log x$$: $$\log x = \frac{\log y}{\log 5}$$.
So $$x = 10^{\frac{\log y}{\log 5}}$$.
We can write this as $$x = \left(10^{\log y}\right)^{1/\log 5} = y^{1/\log 5}$$, since $$10^{\log y} = y$$.
For the inverse function, we swap $$x$$ and $$y$$: $$y = x^{1/\log 5}$$.
This matches Option C: $$y = x^{\frac{1}{\log 5}}$$.
Let $$S = \{1, 2, 3, 4, 5, 6, 7\}$$. Then the number of possible functions $$f : S \rightarrow S$$ such that $$f(m \cdot n) = f(m) \cdot f(n)$$ for every $$m, n \in S$$ and $$m \cdot n \in S$$, is equal to _________.
We are given the set $$S=\{1,2,3,4,5,6,7\}$$ and we must count all functions $$f:S\to S$$ that satisfy the multiplicative rule
$$f(m\cdot n)=f(m)\cdot f(n)$$
for every pair $$m,n\in S$$ for which the product $$m\cdot n$$ is still inside $$S$$. We begin by looking at the special element $$1$$.
Taking $$m=1$$ in the defining property gives the formula
$$f(1\cdot n)=f(1)\cdot f(n).$$
Because $$1\cdot n=n$$, this simplifies to
$$f(n)=f(1)\,f(n)\quad\text{for every }n\in S.$$
The only way this can hold for all $$n$$ (with the values always lying in $$S$$ and hence never being $$0$$) is when
$$f(1)=1.$$
So the value at $$1$$ is completely fixed.
Next we list all products inside $$S$$ that are still in $$S$$. Besides the trivial $$1\cdot n=n$$, only three distinct products appear:
$$2\cdot2=4,\qquad 2\cdot3=6,\qquad 3\cdot2=6.$$
No other product of two elements of $$S$$ stays within $$S$$, because, for instance, $$3\cdot3=9\notin S$$ and $$2\cdot4=8\notin S$$. Therefore the multiplicative rule imposes conditions only on the numbers $$4$$ and $$6$$. Let us introduce the convenient names
$$a=f(2),\qquad b=f(3).$$
Using the rule on each admissible product, we obtain:
1. For $$2\cdot2=4$$ we must have
$$f(4)=f(2\cdot2)=f(2)^2=a^2.$$ 2. For $$2\cdot3=6$$ (and equally for $$3\cdot2=6$$) we must have
$$f(6)=f(2\cdot3)=f(2)\,f(3)=ab.$$
Thus the values of $$f$$ at $$4$$ and $$6$$ are forced once we pick $$a=f(2)$$ and $$b=f(3)$$. In contrast, the values at $$5$$ and $$7$$ are not tied to any product lying in $$S$$, so they may be chosen freely from $$\{1,2,3,4,5,6,7\}$$ later on.
The crucial point is that every value of the function must lie in $$S$$. Hence we need
$$a^2\le 7\quad\text{and}\quad ab\le 7.$$
We now enumerate all possibilities for $$a$$ and $$b$$ satisfying these two inequalities.
• If $$a=1$$, then $$a^2=1\le7$$ automatically, and $$ab=b\le7$$ for every $$b\in\{1,2,3,4,5,6,7\}$$. So with $$a=1$$, we have $$7$$ admissible choices for $$b$$.
• If $$a=2$$, then $$a^2=4\le7$$ is still allowed, but the inequality $$ab\le7$$ becomes $$2b\le7$$, i.e. $$b\le3$$. Hence $$b$$ can be $$1,2,$$ or $$3$$, giving $$3$$ choices.
• If $$a\ge3$$, then $$a^2\ge9>7$$, which violates $$a^2\le7$$, so no further values of $$a$$ are possible.
Combining the two admissible cases, we have in total
$$7+3=10$$
legal pairs $$(a,b)=(f(2),f(3)).$$
After fixing such a pair, the values at $$4$$ and $$6$$ are already determined by $$f(4)=a^2$$ and $$f(6)=ab$$, and they automatically lie in $$S$$ by the way we chose $$a$$ and $$b$$. The final freedom rests with $$f(5)$$ and $$f(7)$$, each of which can be any of the $$7$$ members of $$S$$. Therefore the total number of distinct functions is
$$10\;\times\;7\;\times\;7 \;=\;10\;\times\;49 \;=\;490.$$
So, the answer is $$490$$.
If $$a + \alpha = 1, b + \beta = 2$$ and $$af(x) + \alpha f\left(\frac{1}{x}\right) = bx + \frac{\beta}{x}, x \neq 0$$, then the value of the expression $$\frac{f(x) + f\left(\frac{1}{x}\right)}{x + \frac{1}{x}}$$ is ______.
We are given $$a + \alpha = 1$$, $$b + \beta = 2$$, and the functional equation $$af(x) + \alpha f\!\left(\frac{1}{x}\right) = bx + \frac{\beta}{x}$$ for $$x \neq 0$$.
Replacing $$x$$ with $$\frac{1}{x}$$ in the functional equation gives $$af\!\left(\frac{1}{x}\right) + \alpha f(x) = \frac{b}{x} + \beta x$$.
Adding the original equation and this new equation: $$(a + \alpha)f(x) + (a + \alpha)f\!\left(\frac{1}{x}\right) = (b + \beta)x + (b + \beta)\frac{1}{x}$$, which simplifies to $$(a + \alpha)\left[f(x) + f\!\left(\frac{1}{x}\right)\right] = (b + \beta)\left(x + \frac{1}{x}\right)$$.
Since $$a + \alpha = 1$$ and $$b + \beta = 2$$, we get $$f(x) + f\!\left(\frac{1}{x}\right) = 2\left(x + \frac{1}{x}\right)$$.
Therefore, $$\frac{f(x) + f\!\left(\frac{1}{x}\right)}{x + \frac{1}{x}} = 2$$.
The correct answer is $$2$$.
The contrapositive of the statement "If I reach the station in time, then I will catch the train" is:
First, we identify the logical form of the given English sentence. The sentence “If I reach the station in time, then I will catch the train” can be written in symbolic logic as $$P \rightarrow Q,$$ where
$$P : \text{“I reach the station in time,”}$$ $$Q : \text{“I will catch the train.”}$$
Now, we recall the definition of a contrapositive. For any implication of the form
$$P \rightarrow Q,$$
the contrapositive is obtained by simultaneously negating both parts and reversing their order. Symbolically, the contrapositive is
$$\neg Q \;\rightarrow\; \neg P.$$
Here $$\neg$$ (read “not”) is the logical negation operator. So we proceed step by step.
First we negate the consequent $$Q$$: $$\neg Q : \text{“I will not catch the train.”}$$
Next we negate the antecedent $$P$$: $$\neg P : \text{“I do not reach the station in time.”}$$
Finally, we reverse their order in the implication. Thus the contrapositive of $$P \rightarrow Q$$ is written in words as
“If I will not catch the train, then I do not reach the station in time.”
This matches exactly with Option D.
Hence, the correct answer is Option D.
Which of the following statement is a tautology?
To decide which given statement is a tautology, we consider every option one by one and simplify it algebraically.
First, recall the basic logical equivalence for an implication:
$$a \rightarrow b \;\equiv\; \sim a \;\vee\; b.$$
We will convert each implication using this rule and then simplify.
Option A is $$p \,\vee\, (\sim q) \;\rightarrow\; p \,\wedge\, q.$$
Using the implication rule we have
$$\sim\bigl(p \,\vee\, (\sim q)\bigr) \;\vee\; (p \,\wedge\, q).$$
Apply De Morgan’s law to the negation:
$$\sim p \;\wedge\; q \;\vee\; p \;\wedge\; q.$$
Now take $$q$$ common:
$$q \;\wedge\;(\sim p \;\vee\; p).$$
Inside the parentheses, $$\sim p \;\vee\; p$$ is a tautology (it is always true). Therefore the whole expression reduces to
$$q \;\wedge\; \text{(True)} \;=\; q.$$
This final result $$q$$ is not always true (it is false when $$q$$ is false), so Option A is not a tautology.
Option B is $$\sim(p \,\wedge\, \sim q) \;\rightarrow\; p \,\vee\, q.$$
Convert the implication:
$$\sim\!\bigl(\sim(p \,\wedge\, \sim q)\bigr) \;\vee\; (p \,\vee\, q).$$
The double negation simplifies immediately:
$$(p \,\wedge\, \sim q) \;\vee\; p \;\vee\; q.$$
Group the $$p$$ terms:
$$p \;\vee\; (p \,\wedge\, \sim q) \;\vee\; q.$$
Using the absorption law $$p \,\vee\, (p \,\wedge\, r)=p,$$ we obtain
$$p \;\vee\; q.$$
The expression $$p \;\vee\; q$$ can be false (specifically when $$p$$ and $$q$$ are both false). Thus Option B is not a tautology.
Option C is $$\sim(p \,\vee\, \sim q) \;\rightarrow\; p \,\wedge\, q.$$
Again convert the implication:
$$\sim\!\bigl(\sim(p \,\vee\, \sim q)\bigr) \;\vee\; (p \,\wedge\, q).$$
The double negation gives
$$(p \,\vee\, \sim q) \;\vee\; (p \,\wedge\, q).$$
Take $$p$$ common from the last two pieces:
$$p \;\vee\; \sim q \;\vee\; (p \,\wedge\, q).$$
Using absorption again, $$p \;\vee\; (p \,\wedge\, q)=p$$, so we get
$$p \;\vee\; \sim q.$$
This can be false whenever $$p$$ is false and $$q$$ is true. Hence Option C is not a tautology.
Option D is $$\sim(p \,\vee\, \sim q) \;\rightarrow\; p \,\vee\, q.$$
Convert the implication exactly as before:
$$\sim\!\bigl(\sim(p \,\vee\, \sim q)\bigr) \;\vee\; (p \,\vee\, q).$$
Simplify the double negation:
$$(p \,\vee\, \sim q) \;\vee\; (p \,\vee\, q).$$
Rearrange the terms:
$$p \;\vee\; \sim q \;\vee\; p \;\vee\; q.$$
Using idempotent law $$p \,\vee\, p = p,$$ merge the repeated $$p$$ terms:
$$p \;\vee\; \sim q \;\vee\; q.$$
Now notice that $$\sim q \;\vee\; q$$ is always true (law of excluded middle), so write
$$p \;\vee\; \text{(True)}.$$
Finally, $$\alpha \;\vee\; \text{(True)} = \text{True}$$ for any statement $$\alpha$$. Therefore the whole expression is always true, no matter what truth-values $$p$$ and $$q$$ take.
Thus Option D represents a statement that is true in every possible case; that is exactly the definition of a tautology.
Hence, the correct answer is Option D.
Consider the statement: "For an integer n, if $$n^3 - 1$$ is even, then $$n$$ is odd". The contrapositive statement of this statement is:
We begin with the original conditional statement:
“For an integer $$n$$, if $$n^{3}-1$$ is even, then $$n$$ is odd.”
To form the contrapositive, we first identify its two parts clearly.
Let
$$P : n^{3}-1 \text{ is even}$$
$$Q : n \text{ is odd}$$
The original statement in symbolic form is $$P \Rightarrow Q$$, which reads “If $$P$$, then $$Q$$.”
Now, we recall the definition of a contrapositive. For any implication $$P \Rightarrow Q$$, the contrapositive is obtained by negating both parts and reversing the direction of implication. In symbols, the contrapositive is:
$$\neg Q \Rightarrow \neg P$$
We now write down each negation explicitly.
Negation of $$Q$$:
$$\neg Q : n \text{ is not odd}$$
But for integers, “not odd” is the same as “even.” So we can re-express it as
$$\neg Q : n \text{ is even}$$
Negation of $$P$$:
$$\neg P : n^{3}-1 \text{ is not even}$$
Again, for integers, “not even” means “odd.” Hence we rewrite
$$\neg P : n^{3}-1 \text{ is odd}$$
Substituting these negations into the symbolic form $$\neg Q \Rightarrow \neg P$$, we obtain the contrapositive sentence:
“For an integer $$n$$, if $$n$$ is even, then $$n^{3}-1$$ is odd.”
Looking at the options provided, this matches Option A.
Hence, the correct answer is Option A.
Contrapositive of the statement:
'If a function $$f$$ is differentiable at $$a$$, then it is also continuous at $$a$$', is
We begin with the original statement, which is an implication:
$$P : \text{The function } f \text{ is differentiable at } a$$
$$Q : \text{The function } f \text{ is continuous at } a$$
Stated in words, the implication is “If $$P$$, then $$Q$$” or symbolically $$P \Rightarrow Q$$.
To find its contrapositive, we recall the logical rule:
Formula for contrapositive: For any implication $$P \Rightarrow Q$$, the contrapositive is $$\lnot Q \Rightarrow \lnot P$$.
That is, we first negate the conclusion $$Q$$, then make it the new hypothesis; simultaneously we negate the original hypothesis $$P$$ and make it the new conclusion.
Applying this rule step by step:
1. Negate the conclusion $$Q$$.
The negation of “$$f$$ is continuous at $$a$$” is “$$f$$ is not continuous at $$a$$”.
So $$\lnot Q : \text{The function } f \text{ is not continuous at } a$$.
2. Negate the hypothesis $$P$$.
The negation of “$$f$$ is differentiable at $$a$$” is “$$f$$ is not differentiable at $$a$$”.
So $$\lnot P : \text{The function } f \text{ is not differentiable at } a$$.
3. Form the new implication $$\lnot Q \Rightarrow \lnot P$$.
In sentence form this reads: “If the function $$f$$ is not continuous at $$a$$, then $$f$$ is not differentiable at $$a$$.”
We now compare this derived contrapositive with the given options:
Option A: “If $$f$$ is continuous at $$a$$, then it is not differentiable at $$a$$.” (This is $$Q \Rightarrow \lnot P$$, not the contrapositive.)
Option B: “If $$f$$ is not continuous at $$a$$, then it is not differentiable at $$a$$.” (This matches $$\lnot Q \Rightarrow \lnot P$$ exactly.)
Option C: “If $$f$$ is not continuous at $$a$$, then it is differentiable at $$a$$.” (This is $$\lnot Q \Rightarrow P$$, the inverse of Option A, still incorrect.)
Option D: “If $$f$$ is continuous at $$a$$, then it is differentiable at $$a$$.” (This is simply the converse of the original statement.)
Only Option B reproduces the contrapositive. Hence, the correct answer is Option B.
For two statements $$p$$ and $$q$$, the logical statement $$(p \rightarrow q) \wedge (q \rightarrow \sim p)$$ is equivalent to
We begin with the compound statement
$$ (p \rightarrow q)\;\wedge\;(q \rightarrow \sim p). $$
First, recall the fundamental implication formula
$$ p \rightarrow q \;\equiv\; \sim p \,\vee\, q, $$
which says “if p then q” is logically the same as “either not p or q.” Applying this rule to each implication separately, we obtain
$$ (p \rightarrow q)\;=\;\sim p \,\vee\, q, $$
and
$$ (q \rightarrow \sim p)\;=\;\sim q \,\vee\, \sim p. $$
Therefore our original statement becomes
$$ (\sim p \,\vee\, q)\;\wedge\;(\sim q \,\vee\, \sim p). $$
Observe that both disjunctions contain the term $$\sim p$$, so it is natural to use the distributive law of Boolean algebra, which states
$$ (A \,\vee\, B)\;\wedge\;(A \,\vee\, C) \;\equiv\; A \,\vee\, (B \,\wedge\, C). $$
Here we identify
$$A = \sim p,\qquad B = q,\qquad C = \sim q.$$
Substituting these into the distributive formula, we have
$$ (\sim p \,\vee\, q)\;\wedge\;(\sim p \,\vee\, \sim q) \;\equiv\; \sim p \,\vee\, (q \,\wedge\, \sim q). $$
Now, $$q \,\wedge\, \sim q$$ is a contradiction: one cannot have $$q$$ and “not $$q$$” true at the same time. Thus
$$ q \,\wedge\, \sim q \;\equiv\; \text{False}. $$
Using the identity $$A \,\vee\, \text{False} \equiv A$$, we finally arrive at
$$ \sim p \,\vee\, \text{False} \;\equiv\; \sim p. $$
Hence the entire logical statement simplifies to $$\sim p$$.
Looking at the given options, $$\sim p$$ corresponds to Option C.
Hence, the correct answer is Option C.
Negation of the statement: $$\sqrt{5}$$ is an integer or 5 is irrational is:
We begin by translating the given English sentence into symbols. Let $$P$$ denote the statement “$$\sqrt{5}$$ is an integer.” Let $$Q$$ denote the statement “$$5$$ is irrational.” The original sentence is “$$\sqrt{5}$$ is an integer or 5 is irrational,” which is symbolically $$P \lor Q$$.
To find the negation, we recall the logical rule known as De Morgan’s law. The law states: for any two statements $$P$$ and $$Q$$, $$\neg(P \lor Q) \;=\; (\neg P) \land (\neg Q).$$ In words, “not (P or Q)” is equivalent to “(not P) and (not Q).”
Applying this formula to our case, we have $$\neg(P \lor Q) \;=\; (\neg P) \land (\neg Q).$$
Now we translate each piece back into ordinary language. The negation $$\neg P$$ is “$$\sqrt{5}$$ is not an integer.” The negation $$\neg Q$$ is “5 is not irrational,” i.e. “5 is rational” (indeed 5 is an integer, hence rational).
Combining these two with the connective “and,” we obtain “$$\sqrt{5}$$ is not an integer and 5 is not irrational.”
Examining the choices, this wording matches exactly with Option B.
Hence, the correct answer is Option B.
Given the following two statements:
$$(S_1)$$ : $$(q \vee p) \to (p \leftrightarrow \sim q)$$ is a tautology
$$(S_2)$$ : $$\sim q \wedge (\sim p \leftrightarrow q)$$ is a fallacy. Then:
Let us first write clearly what every symbol means. The symbol $$\vee$$ stands for “or”, $$\wedge$$ for “and”, $$\sim$$ for “not”, $$\to$$ for “if … then …”, and $$\leftrightarrow$$ for “if and only if” (biconditional). A statement is a tautology when it is true for every possible truth-value assignment of its component variables, while it is a fallacy when it is false for every assignment.
We have two compound statements:
$$S_1 :\;(q \vee p) \to (p \leftrightarrow \sim q)$$
$$S_2 :\;\sim q \wedge (\sim p \leftrightarrow q)$$
To test whether $$S_1$$ is a tautology, we enumerate all possible truth-values of $$p$$ and $$q$$. There are four possibilities: $$(p,q) = (T,T),\,(T,F),\,(F,T),\,(F,F).$$ For every pair we shall compute each sub-expression step by step.
Case 1: $$p=T,\;q=T$$
First, $$q \vee p = T \vee T = T.$$
Next, $$\sim q = \sim T = F,$$ so $$p \leftrightarrow \sim q = T \leftrightarrow F = F$$ because a biconditional is true only when both sides have the same truth value.
Finally, $$(q \vee p) \to (p \leftrightarrow \sim q) = T \to F = F,$$ since “true implies false” is false.
Case 2: $$p=T,\;q=F$$
Here, $$q \vee p = F \vee T = T.$$
Also, $$\sim q = \sim F = T,$$ hence $$p \leftrightarrow \sim q = T \leftrightarrow T = T.$$
Thus $$(q \vee p) \to (p \leftrightarrow \sim q) = T \to T = T.$$
Case 3: $$p=F,\;q=T$$
We obtain $$q \vee p = T \vee F = T.$$
Further, $$\sim q = \sim T = F,$$ so $$p \leftrightarrow \sim q = F \leftrightarrow F = T.$$
Consequently, $$(q \vee p) \to (p \leftrightarrow \sim q) = T \to T = T.$$
Case 4: $$p=F,\;q=F$$
Now $$q \vee p = F \vee F = F.$$
Whenever the antecedent of an implication is false, the whole implication is automatically true, because $$F \to X = T$$ for any $$X$$. Therefore we do not even need to calculate the biconditional; still, for completeness we note $$\sim q = T$$ and $$p \leftrightarrow \sim q = F \leftrightarrow T = F.$$ The implication is $$F \to F = T.$$
Collecting the truth values of $$S_1$$ we have: $$F,\;T,\;T,\;T.$$ Because one row (the very first) gives false, $$S_1$$ is not a tautology. So statement $$S_1$$ is incorrect.
Next we examine $$S_2 = \sim q \wedge (\sim p \leftrightarrow q)$$ to see whether it is a fallacy. Again we test all four assignments.
Case 1: $$p=T,\;q=T$$
Compute $$\sim q = F.$$
Compute $$\sim p = F,$$ so $$\sim p \leftrightarrow q = F \leftrightarrow T = F.$$
Hence $$\sim q \wedge (\sim p \leftrightarrow q) = F \wedge F = F.$$
Case 2: $$p=T,\;q=F$$
We get $$\sim q = T.$$
Also $$\sim p = F,$$ and $$\sim p \leftrightarrow q = F \leftrightarrow F = T.$$
Therefore $$\sim q \wedge (\sim p \leftrightarrow q) = T \wedge T = T.$$ This row gives true.
Case 3: $$p=F,\;q=T$$
Here $$\sim q = F.$$
Then $$\sim p = T,$$ and $$\sim p \leftrightarrow q = T \leftrightarrow T = T.$$
Thus $$\sim q \wedge (\sim p \leftrightarrow q) = F \wedge T = F.$$
Case 4: $$p=F,\;q=F$$
Now $$\sim q = T.$$
Also $$\sim p = T,$$ giving $$\sim p \leftrightarrow q = T \leftrightarrow F = F.$$
Hence $$\sim q \wedge (\sim p \leftrightarrow q) = T \wedge F = F.$$
The truth values obtained for $$S_2$$ are $$F,\;T,\;F,\;F.$$ Because at least one row (the second) is true, the statement is not always false; therefore it is not a fallacy. Hence statement $$S_2$$ is also incorrect.
We have shown that $$S_1$$ is not a tautology and $$S_2$$ is not a fallacy. Thus both statements asserted in the question are wrong.
Hence, the correct answer is Option A.
If $$p \to (p \wedge \sim q)$$ is false, then the truth values of $$p$$ and $$q$$ are respectively:
We are told that the proposition $$p \to (p \wedge \sim q)$$ is false.
First, we recall the fundamental rule for a material implication. The compound statement $$A \to B$$ is false only in the single case when the antecedent $$A$$ is true and the consequent $$B$$ is false. Symbolically,
$$A \to B = F \;\; \text{iff} \;\; A = T \text{ and } B = F.$$
In our problem, the antecedent is $$p$$ and the consequent is $$p \wedge \sim q.$$ So, for the whole implication to be false, we must have
$$p = T \quad\text{and}\quad (p \wedge \sim q) = F.$$
We already know from the first part that
$$p = T.$$
Now we must analyze the conjunctive statement $$p \wedge \sim q.$$ A conjunction $$X \wedge Y$$ is true only when both $$X$$ and $$Y$$ are true; otherwise it is false. Here,
$$X = p, \qquad Y = \sim q.$$
We have just found $$p = T.$$ Let us substitute this known value:
$$p \wedge \sim q = T \wedge \sim q.$$
We are told that this entire conjunction is actually false:
$$T \wedge \sim q = F.$$
The only way an expression of the form $$T \wedge Y$$ can be false is when the second factor $$Y$$ is false. Hence,
$$\sim q = F.$$
A negation $$\sim q$$ is false precisely when the original statement $$q$$ is true. Therefore,
$$q = T.$$
Collecting our results, we have obtained
$$p = T, \qquad q = T.$$
This matches Option C, which lists the truth values as $$T, T.$$
Hence, the correct answer is Option 3.
If $$R = \{(x, y) : x, y \in Z, x^2 + 3y^2 \le 8\}$$ is a relation on the set of integers $$Z$$, then the domain of $$R^{-1}$$ is:
First, recall that the inverse relation $$R^{-1}$$ is obtained by interchanging the coordinates of every ordered pair of $$R$$. Consequently, every first component (the “domain”) of $$R^{-1}$$ comes from a second component of some ordered pair in $$R$$. In other words,
$$\text{Domain}(R^{-1})=\text{Range}(R).$$
Therefore we must determine all integer values of $$y$$ for which there exists at least one integer $$x$$ satisfying the inequality that defines $$R$$, namely
$$x^2+3y^2\le 8.$$
We systematically test every integer value of $$y$$ whose square cannot make the left-hand side exceed 8.
Let us examine successive values of $$y$$.
1. Take $$y=0$$. We have $$y^2=0$$, so the inequality becomes
$$x^2+3(0)^2\le 8 \;\Longrightarrow\; x^2\le 8.$$
The integer squares not exceeding 8 are $$0,1,4$$. Thus the corresponding integer values of $$x$$ are
$$x=\,-2,\,-1,\,0,\,1,\,2.$$
Since at least one such $$x$$ exists, $$y=0$$ appears in the range of $$R$$.
2. Next take $$y=1$$. We have $$y^2=1$$, giving
$$x^2+3(1)^2\le 8 \;\Longrightarrow\; x^2+3\le 8 \;\Longrightarrow\; x^2\le 5.$$
The integer squares not exceeding 5 are again $$0,1,4$$, so
$$x=\,-2,\,-1,\,0,\,1,\,2.$$
Hence $$y=1$$ also lies in the range of $$R$$.
3. Because the expression depends on $$y^2$$, the same result holds for $$y=-1$$. Indeed, $$(-1)^2=1$$, so the identical calculation shows at least one suitable $$x$$ exists. Thus $$y=-1$$ is present in the range of $$R$$.
4. Now consider $$y=2$$ or $$y=-2$$. Here $$y^2=4$$, leading to
$$x^2+3(4)\le 8 \;\Longrightarrow\; x^2+12\le 8 \;\Longrightarrow\; x^2\le -4.$$
The inequality $$x^2\le -4$$ has no integer solution because a square is always non-negative. Therefore $$y=\pm2$$ do not belong to the range of $$R$$.
5. For any $$|y|\ge 2$$, the value of $$3y^2$$ is at least 12, which already exceeds 8, so no integer $$x$$ can satisfy the defining inequality. Thus no further $$y$$ values are possible.
Collecting all successful $$y$$ values, we obtain
$$\text{Range}(R)=\{-1,\,0,\,1\}.$$
Therefore
$$\text{Domain}(R^{-1})=\{-1,\,0,\,1\}.$$
Hence, the correct answer is Option D.
Let $$p$$, $$q$$, $$r$$ be three statements such that the truth value of $$(p \wedge q) \to (\sim q \vee r)$$ is $$F$$. Then the truth values of $$p$$, $$q$$, $$r$$ are respectively:
We have the compound statement $$ (p \wedge q) \to (\sim q \vee r) $$ whose truth value is given to be $$F$$ (false).
First, recall the truth rule for an implication. The statement $$A \to B$$ is false only in one situation: when the antecedent $$A$$ is true and simultaneously the consequent $$B$$ is false. In every other case the implication is true.
Here the antecedent is $$p \wedge q$$ and the consequent is $$\sim q \vee r$$. Because the whole implication is false, we must have
$$ p \wedge q = T \quad \text{and} \quad \sim q \vee r = F. $$
Now we analyse each part in turn.
From $$ p \wedge q = T $$, the truth table of conjunction tells us that a conjunction is true only when both components are true. Hence
$$ p = T \quad \text{and} \quad q = T. $$
Next, look at the consequent $$\sim q \vee r$$. We already know $$q = T$$, so its negation is
$$ \sim q = \sim T = F. $$
The consequent simplifies to
$$ \sim q \vee r = F \vee r. $$
The truth table for a disjunction states that $$A \vee B$$ is false only when both $$A$$ and $$B$$ are false. We already have $$F$$ in place of $$A$$, so to make the entire disjunction false we must also have
$$ r = F. $$
Collecting the results, we find
$$ p = T, \; q = T, \; r = F. $$
Checking the option list, this matches Option A.
Hence, the correct answer is Option A.
The negation of the Boolean expression $$p \vee (\sim p \wedge q)$$ is equivalent to:
We are asked to find the negation of the Boolean expression $$p \vee (\sim p \wedge q)$$ and then match the simplified result with one of the given options.
First we write the required negation explicitly:
$$\neg\bigl[p \vee (\sim p \wedge q)\bigr].$$
We recall De Morgan’s first law, which states that for any two propositions $$A$$ and $$B$$, the negation of their disjunction is
$$\neg(A \vee B)=\neg A \wedge \neg B.$$
In our expression, we can treat $$A$$ as $$p$$ and $$B$$ as $$(\sim p \wedge q)$$. Applying the law we get
$$\neg\bigl[p \vee (\sim p \wedge q)\bigr] \;=\; \bigl(\neg p\bigr) \;\wedge\; \neg\bigl(\,\sim p \wedge q\,\bigr).$$
Now we turn to the second negation inside. Again, by De Morgan’s second law, which says
$$\neg(X \wedge Y)=\neg X \vee \neg Y,$$
we let $$X=\sim p$$ and $$Y=q$$. Thus
$$\neg\bigl(\,\sim p \wedge q\,\bigr)=\neg(\sim p) \;\vee\; \neg q.$$
The double negation rule $$\neg(\sim p)=p$$ simplifies the first term, so we have
$$\neg\bigl(\,\sim p \wedge q\,\bigr)=p \;\vee\; \neg q.$$
Substituting this back into the earlier expression yields
$$\bigl(\neg p\bigr) \wedge \bigl(p \;\vee\; \neg q\bigr).$$
We now use the distributive law of conjunction over disjunction, namely
$$X \wedge (Y \vee Z) = (X \wedge Y) \vee (X \wedge Z).$$
Here $$X=\neg p,$$ $$Y=p,$$ and $$Z=\neg q.$$ Distributing gives
$$\bigl(\neg p \wedge p\bigr) \;\vee\; \bigl(\neg p \wedge \neg q\bigr).$$
Observing that $$\neg p \wedge p$$ is always false (a contradiction), we replace it by the constant false value, traditionally denoted by $$0$$. Since $$0 \vee$$ (anything) is just that “anything,” the expression simplifies to
$$\neg p \wedge \neg q.$$
Thus the negation of $$p \vee (\sim p \wedge q)$$ is exactly $$\sim p \wedge \sim q$$, which corresponds to Option B.
Hence, the correct answer is Option B.
The negation of the Boolean expression $$x \leftrightarrow \sim y$$ is equivalent to:
We have to find the negation (logical NOT) of the Boolean statement $$x \leftrightarrow \sim y$$ and then express the result in a simplified disjunctive form so that it can be matched with one of the given options.
First of all, let us recall the standard equivalence for a biconditional. The formula for any two propositions $$p$$ and $$q$$ is:
$$p \leftrightarrow q \;=\; (p \wedge q)\;\vee\;(\sim p \wedge \sim q).$$
Now we apply this rule to the concrete biconditional $$x \leftrightarrow \sim y$$ by replacing $$p$$ with $$x$$ and $$q$$ with $$\sim y$$. Doing so gives:
$$x \leftrightarrow \sim y \;=\; (x \wedge \sim y)\;\vee\;(\sim x \wedge \sim(\sim y)).$$
The double negation inside the second conjunct can be removed with the rule $$\sim(\sim y)=y$$. Hence we get:
$$x \leftrightarrow \sim y \;=\; (x \wedge \sim y)\;\vee\;(\sim x \wedge y).$$
We must now take the negation of the whole expression. So we write:
$$\sim\bigl(x \leftrightarrow \sim y\bigr) \;=\; \sim\Bigl[(x \wedge \sim y)\;\vee\;(\sim x \wedge y)\Bigr].$$
To push the negation inside the parentheses, we invoke De Morgan’s law, which states:
$$\sim(A \vee B)\;=\;(\sim A) \wedge (\sim B).$$
Here $$A$$ is $$x \wedge \sim y$$ and $$B$$ is $$\sim x \wedge y$$. Therefore:
$$\sim\Bigl[(x \wedge \sim y)\;\vee\;(\sim x \wedge y)\Bigr] \;=\; \bigl[\sim(x \wedge \sim y)\bigr] \;\wedge\; \bigl[\sim(\sim x \wedge y)\bigr].$$
The next step is to remove each inner negation. Again, we apply De Morgan’s law, this time in the form $$\sim(A \wedge B) = (\sim A) \vee (\sim B).$$ For the first bracket we have $$A = x$$ and $$B = \sim y$$:
$$\sim(x \wedge \sim y) \;=\; (\sim x) \;\vee\; (\sim(\sim y)) \;=\; (\sim x) \vee y.$$
For the second bracket we have $$A = \sim x$$ and $$B = y$$:
$$\sim(\sim x \wedge y) \;=\; (\sim(\sim x)) \;\vee\; (\sim y) \;=\; x \vee (\sim y).$$
So the entire expression is now
$$\bigl[(\sim x) \vee y\bigr] \;\wedge\; \bigl[x \vee (\sim y)\bigr].$$
To simplify, we distribute the conjunction across the disjunctions. The distributive law tells us:
$$(A \vee B)\wedge(C \vee D) \;=\; (A \wedge C)\;\vee\;(A \wedge D)\;\vee\;(B \wedge C)\;\vee\;(B \wedge D).$$
Letting $$A = \sim x,\; B = y,\; C = x,\; D = \sim y,$$ we compute each product term one by one:
1. $$(\sim x) \wedge x = \text{False},$$ because a proposition and its negation cannot both be true.
2. $$(\sim x) \wedge (\sim y) = \sim x \wedge \sim y.$$
3. $$y \wedge x = x \wedge y.$$
4. $$y \wedge (\sim y) = \text{False},$$ again because a variable and its negation cannot both be true.
Combining the surviving non-false terms under disjunction gives:
$$(\sim x \wedge \sim y)\;\vee\;(x \wedge y).$$
Conventionally we write the positive term first, so we obtain the final simplified negation as:
$$ (x \wedge y)\;\vee\;(\sim x \wedge \sim y). $$
Now we match this with the options provided. Option B is exactly
$$(x \wedge y) \vee (\sim x \wedge \sim y).$$
Hence, the correct answer is Option 2.
The proposition $$p \to \sim(p \wedge \sim q)$$ is equivalent to:
We have to simplify the proposition $$p \to \sim(p \wedge \sim q)$$ and then compare the final result with the four given options.
First recall the logical equivalence for an implication. The standard formula is:
$$a \to b \equiv (\sim a) \vee b.$$
In our problem the role of $$a$$ is played by $$p$$ and the role of $$b$$ is played by $$\sim(p \wedge \sim q).$$ Substituting into the formula we obtain
$$p \to \sim(p \wedge \sim q) \equiv (\sim p) \vee \bigl[\;\sim(p \wedge \sim q)\bigr].$$
Now we tackle the term $$\sim(p \wedge \sim q)$$. To simplify a negation of a conjunction, we use De Morgan’s law, which states:
$$\sim(A \wedge B) \equiv (\sim A) \vee (\sim B).$$
Here $$A$$ is $$p$$ and $$B$$ is $$\sim q$$. Applying the law carefully gives
$$\sim(p \wedge \sim q) \equiv (\sim p) \vee \bigl[\sim(\sim q)\bigr].$$
A double negation disappears, because $$\sim(\sim q) \equiv q$$. Hence the entire right-hand side becomes
$$\sim(p \wedge \sim q) \equiv (\sim p) \vee q.$$
We now substitute this back into the expression we obtained after the implication step:
$$(\sim p) \vee \bigl[\;\sim(p \wedge \sim q)\bigr] \equiv (\sim p) \vee \bigl[(\sim p) \vee q\bigr].$$
The disjunction is associative and idempotent, meaning that repeating the same statement inside a string of ORs does not change the result. Explicitly,
$$ (\sim p) \vee (\sim p) \equiv \sim p, \quad\text{and}\quad (\sim p) \vee \bigl[(\sim p) \vee q\bigr] \equiv (\sim p) \vee q.$$
Therefore the original proposition simplifies all the way down to
$$p \to \sim(p \wedge \sim q) \equiv (\sim p) \vee q.$$
This final expression matches exactly what is written in Option B. Hence, the correct answer is Option B.
Which one of the following is a tautology?
We want to know which of the given compound statements is a tautology, that is, which statement is always true no matter which truth-values (T or F) we assign to the simple propositions $$p$$ and $$q$$. The straightforward way is to construct truth-tables for every option, but often we can save time by using well-known logical equivalences. Nevertheless, for absolute clarity we shall give every algebraic step and also exhibit at least one counter-example for all the non-tautological options.
First recall some standard logical facts that we shall need:
1. Implication equivalence $$p \rightarrow q \;\;\text{is equivalent to}\;\; \neg p \vee q$$ (Because an implication is false only when $$p$$ is true and $$q$$ is false.)
2. Distributive, associative, commutative and absorption laws for $$\vee$$ (OR) and $$\wedge$$ (AND) behave exactly like their algebraic counterparts, but with the understanding that TRUE behaves like 1 and FALSE like 0.
3. The absorption laws that we shall use twice are $$p \vee (p \wedge q) \equiv p$$ $$p \wedge (p \vee q) \equiv p.$$ These tell us that mixing a statement with itself inside an OR or an AND does not add any new logical content: $$p$$ already captures the whole truth of the compound.
Now we treat every option one by one.
Option A : $$ (p \wedge (p \rightarrow q)) \rightarrow q $$
We start by rewriting the implication inside the antecedent ($$p \rightarrow q$$) using fact 1.
So, $$p \rightarrow q \equiv \neg p \vee q.$$
Substituting this inside the main expression gives
$$ (p \wedge (\,\neg p \vee q\,)) \rightarrow q. $$
Next we simplify the bracket $$p \wedge (\,\neg p \vee q\,)$$ by distributing $$p$$ over the parentheses:
$$ p \wedge (\,\neg p \vee q\,) \equiv (p \wedge \neg p) \;\vee\; (p \wedge q). $$
But $$p \wedge \neg p$$ is always FALSE (a contradiction), hence
$$ (p \wedge \neg p) \;\vee\; (p \wedge q) \equiv \text{FALSE} \;\vee\; (p \wedge q) \equiv p \wedge q, $$
because OR with FALSE leaves the other term unchanged.
So up to now we have reduced the whole statement to
$$ (p \wedge q) \rightarrow q. $$
Once again we use fact 1 on the outer implication, i.e.
$$ (p \wedge q) \rightarrow q \equiv \neg (p \wedge q) \;\vee\; q. $$
We apply De Morgan to the negation:
$$ \neg (p \wedge q) \equiv \neg p \vee \neg q, $$
so the expression becomes
$$ (\neg p \vee \neg q) \;\vee\; q. $$
OR is associative and commutative, therefore we can rearrange freely. We now gather the two clauses that contain $$q$$:
$$ (\neg p \vee \neg q \vee q) \equiv (\neg p \vee \text{TRUE}), $$
because $$\neg q \vee q$$ is always TRUE. And of course $$\neg p \vee \text{TRUE}$$ simplifies to TRUE (OR with TRUE is TRUE).
Thus the entire compound statement has simplified to the constant truth-value TRUE for every truth assignment to $$p$$ and $$q$$. Therefore option A is a tautology.
Option B : $$ q \rightarrow (p \wedge (p \rightarrow q)) $$
Again write $$p \rightarrow q$$ as $$\neg p \vee q$$ and substitute:
$$ q \rightarrow \bigl(p \wedge (\neg p \vee q)\bigr). $$
As in option A we know that $$p \wedge (\neg p \vee q) \equiv p \wedge q.$$ So we obtain
$$ q \rightarrow (p \wedge q). $$
This implication is equivalent to $$\neg q \vee (p \wedge q).$$ Now choose a valuation with $$q = \text{T}$$ and $$p = \text{F}.$$ Then $$\neg q = \text{F}$$ and $$p \wedge q = \text{F}$$, so the whole expression evaluates to FALSE. Hence option B is not a tautology.
Option C : $$ p \wedge (p \vee q) $$
Using the absorption law stated earlier, we get directly
$$ p \wedge (p \vee q) \equiv p. $$
The value of $$p$$ obviously depends on our choice of truth-values; it is TRUE for $$p = \text{T}$$ and FALSE for $$p = \text{F}$$. Therefore this compound statement sometimes becomes FALSE, so it is not a tautology.
Option D : $$ p \vee (p \wedge q) $$
This is the other absorption law:
$$ p \vee (p \wedge q) \equiv p. $$
Again the truth of the whole expression varies with the truth of $$p$$, so option D is not a tautology.
After examining every choice we see that only option A is always TRUE, i.e. is a tautology.
Hence, the correct answer is Option A.
The statement $$(p \to (q \to p)) \to (p \to (p \vee q))$$ is:
We have to decide the logical nature of the formula $$S=(p\to(q\to p))\to(p\to(p\vee q)).$$
First, we recall the standard implication-disjunction equivalence:
$$a\to b\;\equiv\;\sim a\;\vee\;b.$$
We apply this rule to the innermost implication $$q\to p.$$
So, $$q\to p\;\equiv\;\sim q\;\vee\;p.$$
Substituting this result back into the left part of $$S$$ we get
$$p\to(q\to p)\;\equiv\;p\to(\sim q\vee p).$$
Once again using the same rule $$a\to b\equiv\sim a\vee b$$ on the implication whose antecedent is $$p$$, we have
$$p\to(\sim q\vee p)\;\equiv\;\sim p\;\vee\;(\sim q\;\vee\;p).$$
Now we re-arrange the disjunction because disjunction is associative and commutative:
$$\sim p\;\vee\;(\sim q\;\vee\;p)\;=\;(\sim p\;\vee\;p)\;\vee\;\sim q.$$
We know that the law of excluded middle tells us $$\sim p\;\vee\;p\equiv \text{True}.$$ Therefore,
$$(\sim p\;\vee\;p)\;\vee\;\sim q\;\equiv\;\text{True}\;\vee\;\sim q\;\equiv\;\text{True}.$$
Hence, the whole sub-formula $$p\to(q\to p)$$ is always true; it is a tautology. We can now write
$$p\to(q\to p)\;\equiv\;\text{True}.$$
Next, we turn to the right part of $$S$$, namely $$p\to(p\vee q).$$ Again we use $$a\to b\equiv\sim a\vee b.$$ So,
$$p\to(p\vee q)\;\equiv\;\sim p\;\vee\;(p\vee q).$$
Associating the disjunctions yields
$$\sim p\;\vee\;p\;\vee\;q.$$
By the law of excluded middle, $$\sim p\;\vee\;p\equiv\text{True},$$ hence
$$\sim p\;\vee\;p\;\vee\;q\;\equiv\;\text{True}\;\vee\;q\;\equiv\;\text{True}.$$
Therefore, the consequent $$(p\to(p\vee q))$$ is also a tautology. We can thus rewrite $$S$$ purely in terms of truth values:
$$S\;\equiv\;(\text{True})\;\to\;(\text{True}).$$
Finally, we know that $$\text{True}\to\text{True}\equiv\text{True},$$ because an implication with a true antecedent and a true consequent is true.
So the entire statement $$S$$ is always true for every possible truth-value assignment of $$p$$ and $$q$$. That is, $$S$$ is a tautology.
Hence, the correct answer is Option 4.
For a suitably chosen real constant $$a$$, let a function, $$f : \mathbb{R} - \{-a\} \to \mathbb{R}$$ be defined by $$f(x) = \frac{a-x}{a+x}$$. Further suppose that for any real number $$x \neq -a$$, and $$f(x) \neq -a$$, $$(f \circ f)(x) = x$$. Then $$f\left(-\frac{1}{2}\right)$$ is equal to:
First we recall that the composite function $$(f \circ f)(x)$$ means “apply $$f$$ twice”, i.e. $$(f \circ f)(x)=f\bigl(f(x)\bigr).$$ The statement of the question says that this composite equals $$x$$ itself. Symbolically, for every real $$x \neq -a$$ with $$f(x)\neq -a,$$ we have the requirement
$$f\bigl(f(x)\bigr)=x.$$
Such a function is called an involution. We shall use this condition to determine the constant $$a$$ and then evaluate $$f\!\left(-\dfrac12\right).$$
The given function is
$$f(x)=\dfrac{a-x}{\,a+x\,}.$$
We first compute $$y=f(x):$$
$$y=\dfrac{a-x}{a+x}.$$
Now we apply $$f$$ again, replacing its argument by $$y$$. Thus
$$f\bigl(f(x)\bigr)=\dfrac{a-y}{\,a+y\,}.$$
Substituting $$y=\dfrac{a-x}{a+x}$$ we obtain
$$f\bigl(f(x)\bigr)=\dfrac{a-\dfrac{a-x}{a+x}}{\,a+\dfrac{a-x}{a+x}\,}.$$
To simplify, we bring every term over the common denominator $$(a+x).$$ For the numerator:
$$a-\dfrac{a-x}{a+x}=\dfrac{a(a+x)-(a-x)}{a+x}=\dfrac{a^2+ax-a+x}{a+x}.$$
Collecting like terms gives
$$a^2+ax-a+x=a^2-a+x(a+1).$$
So the numerator equals
$$\dfrac{a^2-a+x(a+1)}{a+x}.$$
For the denominator:
$$a+\dfrac{a-x}{a+x}=\dfrac{a(a+x)+(a-x)}{a+x}=\dfrac{a^2+ax+a-x}{a+x}.$$
Collecting like terms gives
$$a^2+ax+a-x=a^2+a+x(a-1).$$
Hence the denominator equals
$$\dfrac{a^2+a+x(a-1)}{a+x}.$$
Therefore
$$f\bigl(f(x)\bigr)=\dfrac{\dfrac{a^2-a+x(a+1)}{a+x}}{\dfrac{a^2+a+x(a-1)}{a+x}}=\dfrac{a^2-a+x(a+1)}{a^2+a+x(a-1)}.$$
The requirement $$f\bigl(f(x)\bigr)=x$$ now becomes the identity
$$\dfrac{a^2-a+x(a+1)}{a^2+a+x(a-1)}=x \quad \text{for all admissible } x.$$
Cross-multiplying (which is valid because denominators are non-zero away from the excluded points) we get
$$a^2-a+x(a+1)=x\bigl[a^2+a+x(a-1)\bigr].$$
Expanding the right-hand side yields
$$a^2-a+x(a+1)=a^2x+ax+(a-1)x^2.$$
Now we bring every term to the right so that the left side becomes zero, collecting like powers of $$x$$:
$$0=a^2x+ax+(a-1)x^2-\bigl(a^2-a+ax+x\bigr).$$
Distributing the negative sign and combining terms one by one, we obtain
$$0=\underbrace{(a-1)}_{\text{coefficient of }x^2}x^2+\underbrace{\bigl(a^2-1\bigr)}_{\text{coefficient of }x}x+\underbrace{\bigl(-a(a-1)\bigr)}_{\text{constant term}}.$$
For the polynomial to be identically zero for all real $$x,$$ each individual coefficient must vanish:
$$a-1=0,\qquad a^2-1=0,\qquad -a(a-1)=0.$$
The first of these directly gives $$a=1.$$ Substituting $$a=1$$ into the second and third equations confirms that they are also satisfied. Thus the only admissible constant is
$$a=1.$$
With this value, the original function becomes
$$f(x)=\dfrac{1-x}{\,1+x\,}.$$
We are required to evaluate $$f\!\left(-\dfrac12\right).$$ Substituting $$x=-\dfrac12$$ gives
$$f\!\left(-\dfrac12\right)=\dfrac{1-\left(-\dfrac12\right)}{1+\left(-\dfrac12\right)}=\dfrac{1+\dfrac12}{1-\dfrac12}=\dfrac{\dfrac32}{\dfrac12}.$$
Dividing the two fractions, we obtain
$$f\!\left(-\dfrac12\right)=\dfrac32 \times \dfrac21=3.$$
Hence, the correct answer is Option D.
If $$g(x) = x^2 + x - 1$$ and $$(g \circ f)(x) = 4x^2 - 10x + 5$$, then $$f\left(\frac{5}{4}\right)$$ is equal to
We have $$g(x)=x^2+x-1$$ and the composition $$\bigl(g\circ f\bigr)(x)=g\!\bigl(f(x)\bigr)=4x^2-10x+5.$$
Writing $$y=f(x),$$ the definition of composition gives us
$$g\!\bigl(f(x)\bigr)=g(y)=y^2+y-1.$$
But by the statement of the problem the same quantity also equals $$4x^2-10x+5.$$ Hence we must have
$$y^2+y-1=4x^2-10x+5.$$
Substituting back $$y=f(x)$$ we get a quadratic equation in $$f(x):$$
$$\bigl(f(x)\bigr)^2+f(x)-1=4x^2-10x+5.$$
Now we bring every term to the left‐hand side:
$$\bigl(f(x)\bigr)^2+f(x)-1-4x^2+10x-5=0,$$
so
$$\bigl(f(x)\bigr)^2+f(x)-4x^2+10x-6=0.$$
This is a quadratic in the unknown $$f(x).$$ For a quadratic $$at^2+bt+c=0$$ the roots are given by the quadratic formula $$t=\dfrac{-b\pm\sqrt{\,b^2-4ac\,}}{2a}.$$
Here $$a=1,\;b=1,\;c=-4x^2+10x-6,$$ so
$$f(x)=\dfrac{-1\pm\sqrt{\,1-4\bigl(-4x^2+10x-6\bigr)\,}}{2}.$$
Inside the square root we simplify step by step:
$$1-4\bigl(-4x^2+10x-6\bigr)=1+16x^2-40x+24.$$
Combining like terms gives
$$16x^2-40x+25.$$
Recognising a perfect square, we note $$16x^2-40x+25=(4x-5)^2.$$ Hence
$$f(x)=\dfrac{-1\pm|4x-5|}{2}.$$
The two possible expressions that come out are obtained very easily:
If $$|4x-5|=4x-5$$ we get $$f(x)=\dfrac{-1+(4x-5)}{2}=2x-3,$$ and if $$|4x-5|=5-4x$$ we get $$f(x)=\dfrac{-1+(5-4x)}{2}=2-2x.$$
Thus for every $$x$$ the value of $$f(x)$$ is either $$2x-3$$ or $$2-2x.$$ Both of these, when put back into $$g(x),$$ reproduce $$4x^2-10x+5,$$ so the composition condition is satisfied in either case.
Now we specifically need $$f\!\left(\dfrac54\right).$$ Substituting $$x=\dfrac54$$ in either expression:
Using $$f(x)=2x-3,$$ we get $$f\!\left(\dfrac54\right)=2\left(\dfrac54\right)-3=\dfrac{10}{4}-3=\dfrac{5}{2}-3=-\dfrac12.$$
Using $$f(x)=2-2x,$$ we get $$f\!\left(\dfrac54\right)=2-2\left(\dfrac54\right)=2-\dfrac{10}{4}=2-\dfrac{5}{2}=-\dfrac12.$$
Both routes give the same numerical answer, so unambiguously
$$f\!\left(\dfrac54\right)=-\dfrac12.$$
Hence, the correct answer is Option B.
Let $$f : (1, 3) \rightarrow R$$, be a function defined by $$f(x) = \frac{x[x]}{1+x^2}$$, where $$[x]$$ denotes the greatest integer $$\le x$$. Then the range of $$f$$, is
We have the function $$f:(1,3)\rightarrow \mathbb R$$ defined by
$$f(x)=\dfrac{x\,[x]}{1+x^{2}},$$
where $$[x]$$ denotes the greatest integer less than or equal to $$x$$. Because the domain is the open interval $$(1,3)$$, the only possible integer values of $$[x]$$ inside this interval are $$1$$ and $$2$$. So we split the domain into two parts.
First part - when $$1<x<2$$ we have $$[x]=1$$. Substituting this in the formula gives
$$f(x)=\dfrac{x\cdot1}{1+x^{2}}=\dfrac{x}{1+x^{2}}\qquad(1<x<2).$$
To find its range we differentiate. Using the quotient rule $$\displaystyle\left(\dfrac{u}{v}\right)'=\dfrac{u'v-uv'}{v^{2}},$$ with $$u=x,\;u'=1,\;v=1+x^{2},\;v' = 2x,$$ we get
$$f'(x)=\dfrac{1(1+x^{2})-x(2x)}{(1+x^{2})^{2}}=\dfrac{1+x^{2}-2x^{2}}{(1+x^{2})^{2}}=\dfrac{1-x^{2}}{(1+x^{2})^{2}}.$$
Inside the interval $$1<x<2$$ we have $$x^{2}>1$$, so $$1-x^{2}<0$$ and hence $$f'(x)<0$$. Thus $$f(x)=\dfrac{x}{1+x^{2}}$$ is strictly decreasing on $$(1,2)$$.
Because it is decreasing, its largest value occurs as $$x\to1^{+}$$ and its smallest value occurs as $$x\to2^{-}$$. Evaluating the limits,
$$\lim_{x\to1^{+}}\dfrac{x}{1+x^{2}}=\dfrac{1}{1+1}=\dfrac12,$$
$$\lim_{x\to2^{-}}\dfrac{x}{1+x^{2}}=\dfrac{2}{1+4}=\dfrac25.$$
Neither endpoint is actually in the open interval $$(1,2)$$, so neither value is attained. Therefore the range of the first part is
$$\left(\dfrac25,\;\dfrac12\right).$$
Second part - when $$2\le x<3$$ we have $$[x]=2$$. So now
$$f(x)=\dfrac{x\cdot2}{1+x^{2}}=\dfrac{2x}{1+x^{2}}\qquad(2\le x<3).$$
Again we differentiate. Put $$u=2x,\;u'=2,\;v=1+x^{2},\;v'=2x,$$ then
$$f'(x)=\dfrac{2(1+x^{2})-2x(2x)}{(1+x^{2})^{2}}=\dfrac{2+2x^{2}-4x^{2}}{(1+x^{2})^{2}}=\dfrac{2-2x^{2}}{(1+x^{2})^{2}}=\dfrac{2(1-x^{2})}{(1+x^{2})^{2}}.$$
On the interval $$2\le x<3$$ we have $$x^{2}>1$$, so again $$1-x^{2}<0$$ and hence $$f'(x)<0$$ throughout. Thus $$f(x)=\dfrac{2x}{1+x^{2}}$$ is also strictly decreasing on $$[2,3)$$.
The largest value of this part is taken at the left end $$x=2$$ (which is in the domain), and the smallest value is approached as $$x\to3^{-}$$. Compute
$$f(2)=\dfrac{2\cdot2}{1+2^{2}}=\dfrac{4}{1+4}=\dfrac45,$$
$$\lim_{x\to3^{-}}\dfrac{2x}{1+x^{2}}=\dfrac{2\cdot3}{1+3^{2}}=\dfrac{6}{10}=\dfrac35.$$
The value $$\dfrac45$$ is included because $$x=2$$ belongs to the domain; the value $$\dfrac35$$ is not included because $$x=3$$ is not in the domain. Hence the range of the second part is
$$\left(\dfrac35,\;\dfrac45\right].$$
Combining both parts we unite their ranges:
$$\left(\dfrac25,\;\dfrac12\right)\;\cup\;\left(\dfrac35,\;\dfrac45\right].$$
This set matches exactly the interval collection given in Option B.
Hence, the correct answer is Option B.
Which of the following is a tautology?
We recall that a statement is called a tautology when it remains true for every possible truth-value assignment of its component propositions. We shall examine each option one by one, reducing the compound statement with standard logical identities and looking for a possible counter-example. If even a single assignment makes the statement false, then it is not a tautology.
We begin with Option A:
$$ (\sim p)\;\wedge\;(p \vee q)\;\to\; q $$
First we simplify the antecedent "$$(\sim p)\wedge (p\vee q)$$". Using the distributive law
$$ a\wedge(b\vee c)\;=\;(a\wedge b)\;\vee\;(a\wedge c), $$
with $$a=\sim p,\; b=p,\; c=q,$$ we obtain
$$ (\sim p)\wedge(p\vee q)\;=\;[(\sim p)\wedge p] \;\vee\;[(\sim p)\wedge q]. $$
Now $$ (\sim p)\wedge p $$ is a contradiction, i.e. it is always false, so it may be dropped from the disjunction:
$$ (\sim p)\wedge(p\vee q)\;=\;(\sim p)\wedge q. $$
Therefore Option A becomes
$$ [(\sim p)\wedge q]\;\to\;q. $$
Next we recall the definition of implication:
$$ a\to b\;\equiv\;\sim a\;\vee\;b. $$
Replacing $$a$$ with $$ (\sim p)\wedge q $$ and $$b$$ with $$q$$ gives
$$ [(\sim p)\wedge q]\;\to\;q\;\equiv\;\sim[(\sim p)\wedge q]\;\vee\;q. $$
Apply De Morgan’s law to the negation inside:
$$ \sim[(\sim p)\wedge q]\;=\;\sim(\sim p)\;\vee\;\sim q\;=\;p\;\vee\;\sim q. $$
So the whole expression is
$$ (p\;\vee\;\sim q)\;\vee\;q. $$
The associative and commutative laws for disjunction permit us to regroup and obtain
$$ p\;\vee\;(q\;\vee\;\sim q). $$
Within the parentheses, $$ q\;\vee\;\sim q $$ is the law of excluded middle, which is always true, i.e. a tautology $$T$$. Hence we have
$$ p\;\vee\;T\;=\;T. $$
Thus Option A simplifies to a statement that is invariably true, making it a tautology.
Now we test Option B:
$$ (q\to p)\;\vee\;\sim(p\to q). $$
First expand each implication using $$a\to b \equiv \sim a\;\vee\;b$$:
$$ (q\to p) = (\sim q)\;\vee\;p, \qquad (p\to q) = (\sim p)\;\vee\;q.$$ Hence
$$ \sim(p\to q) = \sim[(\sim p)\vee q] = p\wedge\sim q $$ by De Morgan’s law. Therefore Option B becomes
$$ (\sim q\;\vee\;p)\;\vee\;(p\wedge\sim q). $$
We look for a truth-value combination that makes the whole disjunction false. A disjunction is false only when each of its components is false. So we need
$$ \sim q\;\vee\;p = F, \quad\text{and}\quad p\wedge\sim q = F. $$
Take $$p = F$$ and $$q = T$$. Then
$$\sim q = F,\quad p = F,\quad \therefore \sim q\;\vee\;p = F.$$ Also $$p\wedge\sim q = F\wedge F = F.$$ Both parts are false, so the entire statement is false for this assignment. Hence Option B is not a tautology.
Next we inspect Option C:
$$ (\sim q)\;\vee\;(p\wedge q)\;\to\;q. $$
Choose $$q = F$$ (i.e. $$q$$ is false). Then $$\sim q = T$$, so the antecedent $$(\sim q)\;\vee\;(p\wedge q)$$ is true irrespective of $$p$$. The consequent $$q$$, however, is false. Therefore the implication becomes $$T\to F,$$ which is false. So Option C is also not a tautology.
Finally Option D:
$$ (p\to q)\;\wedge\;(q\to p). $$
This is logically equivalent to the biconditional $$p\leftrightarrow q,$$ which is true only when $$p$$ and $$q$$ share the same truth value. Take $$p = T,\, q = F$$. Then $$p\to q = F$$, so the whole conjunction is false. Consequently Option D is not a tautology.
Only Option A survives every test and is always true.
Hence, the correct answer is Option A.
The inverse function of $$f(x) = \frac{8^{2x} - 8^{-2x}}{8^{2x} + 8^{-2x}}$$, $$x \in (-1, 1)$$, is
Let us begin by writing the given relation in a form that can be inverted. We put
$$y \;=\; f(x)\;=\;\frac{8^{2x}-8^{-2x}}{8^{2x}+8^{-2x}},\qquad x\in(-1,1).$$
To clear the negative exponent we multiply the numerator and the denominator by $$8^{2x}$$. This gives
$$y \;=\;\frac{8^{2x}\!\cdot\!8^{2x}\;-\;1}{8^{2x}\!\cdot\!8^{2x}\;+\;1}\;=\;\frac{8^{4x}-1}{8^{4x}+1}.$$
Now we eliminate the fraction by cross-multiplication:
$$y\bigl(8^{4x}+1\bigr)=8^{4x}-1.$$
Expanding the left side we obtain
$$y\cdot8^{4x}+y \;=\;8^{4x}-1.$$
We bring all terms containing $$8^{4x}$$ to one side and the constants to the other side:
$$y\cdot8^{4x}-8^{4x} \;=\;-1-y.$$
Factoring out $$8^{4x}$$ on the left gives
$$8^{4x}(y-1)\;=\;-(1+y).$$
We divide by $$y-1$$ (remembering that $$y\neq1$$ inside the interval of definition) and, at the same time, remove the minus sign from numerator and denominator:
$$8^{4x}\;=\;\frac{-(1+y)}{\,y-1\,}\;=\;\frac{1+y}{1-y}.$$
The base-exponent form $$a^m=b$$ can always be rewritten as the logarithmic form $$m=\log_a b$$. Applying this rule with base $$8$$ we take logarithm base $$8$$ of both sides:
$$4x\;=\;\log_8\!\left(\frac{1+y}{1-y}\right).$$
Dividing by $$4$$ produces
$$x\;=\;\frac14\,\log_8\!\left(\frac{1+y}{1-y}\right).$$
Up to this point $$y$$ was the original output and $$x$$ was the original input. For the inverse function we interchange their roles, writing the final answer as
$$f^{-1}(x)\;=\;\frac14\,\log_8\!\left(\frac{1+x}{1-x}\right).$$
This expression exactly matches Option D.
Hence, the correct answer is Option D.
Let $$A = \{a, b, c\}$$ and $$B = \{1, 2, 3, 4\}$$. Then the number of elements in the set $$C = \{f : A \to B \mid 2 \in f(A)$$ and $$f$$ is not one-one$$\}$$ is...
We have $$A = \{a,\; b,\; c\}$$ so $$|A| = 3$$, and $$B = \{1,\; 2,\; 3,\; 4\}$$ so $$|B| = 4$$. A function $$f : A \to B$$ assigns to every element of $$A$$ exactly one element of $$B$$.
First, recall that the total number of all possible functions from a set with $$m$$ elements to a set with $$n$$ elements is $$n^{\,m}$$ because each element of the domain has $$n$$ independent choices. Here, $$m = 3$$ and $$n = 4$$, so the total number of functions is
$$4^{\,3} = 64.$$
We are interested only in those functions which satisfy two simultaneous conditions:
(i) $$2 \in f(A)\;,$$ meaning that at least one element of $$A$$ is mapped to $$2$$.
(ii) $$f$$ is not one-one (not injective), i.e. at least two elements of $$A$$ share the same image.
We shall count functions satisfying (i) first, then remove those that violate (ii). Let us denote by $$N_1$$ the number of functions satisfying (i) and by $$N_{1,\,\text{inj}}$$ the number of those functions which are also injective. The desired count will therefore be
$$N = N_1 \;-\; N_{1,\,\text{inj}}.$$
Counting $$N_1$$ - functions with $$2$$ in the image.
Consider the complementary set of functions where $$2$$ never appears. For every element of $$A$$ we then have only $$\{1,3,4\}$$ available, that is $$3$$ choices per element. Hence the number of such functions is
$$3^{\,3} = 27.$$
By subtraction, the number of functions that do include $$2$$ is
$$N_1 = 64 \;-\; 27 = 37.$$
Counting $$N_{1,\,\text{inj}}$$ - injective functions with $$2$$ in the image.
A function from a set of $$3$$ elements to a set of $$4$$ elements is injective exactly when it assigns three distinct images. The total number of injective functions is therefore the number of permutations of any $$3$$ distinct elements chosen from $$4$$, which is the permutation number
$$P(4,3) = 4 \times 3 \times 2 = 24.$$
Among these, let us identify how many avoid the value $$2$$ entirely; such functions must use the three values $$1,3,4$$. There is only one way to choose these three values, and they can be arranged in $$P(3,3) = 3 \times 2 \times 1 = 6$$ ways. Hence
$$\text{Injective functions without }2 = 6.$$
Consequently, the injective functions that do contain $$2$$ are
$$N_{1,\,\text{inj}} = 24 \;-\; 6 = 18.$$
Final subtraction.
We now exclude these $$18$$ injective functions from the $$37$$ functions that contain $$2$$:
$$N = 37 \;-\; 18 = 19.$$
So, the answer is $$19$$.
Contrapositive of the statement "If two numbers are not equal, then their squares are not equal" is:
We begin by recalling the basic logical rule for conditional statements. For any implication of the form $$p \rightarrow q,$$ the contrapositive is obtained by first negating the conclusion $$q$$ and then making this negation the hypothesis, while simultaneously negating the original hypothesis $$p$$ and making this negation the new conclusion. Symbolically, the rule is stated as:
$$\text{If } p \rightarrow q,$$ then its contrapositive is $$\; \lnot q \rightarrow \lnot p.$$
Now we identify the parts of the given English sentence. The original statement is:
“If two numbers are not equal, then their squares are not equal.”
We translate this into symbolic form. Let
$$p : \text{“the two numbers are not equal”},$$ $$q :$$ “the squares of the two numbers are not equal” $$.$$
Thus the given statement is precisely $$p \rightarrow q.$$
To form the contrapositive, we negate $$q$$ and $$p$$ in turn:
First the negation of $$q$$ is
$$\lnot q :$$ “the squares of the two numbers are equal” $$.$$
Second the negation of $$p$$ is
$$\lnot p : \text{“the two numbers are equal”}.$$
Applying the rule $$\lnot q \rightarrow \lnot p,$$ we obtain the contrapositive sentence in everyday language:
“If the squares of two numbers are equal, then the numbers are equal.”
Now we compare this derived sentence with the options provided. Option C reads:
“If the squares of two numbers are equal, then the numbers are equal.”
This matches word for word with our contrapositive.
Hence, the correct answer is Option C.
For any two statement $$p$$ and $$q$$, the negative of the expression $$p \lor (\sim p \land q)$$ is:
We begin with the given propositional expression
$$E \;=\; p \,\lor\, (\sim p \,\land\, q).$$
Our task is to find the negation $$\sim E$$ and then match it with the choices. To do this comfortably, it is convenient first to simplify $$E$$ itself.
We recall the distributive law of propositional logic, stated as
$$A \,\lor\, (B \,\land\, C)\;=\; (A \,\lor\, B)\,\land\,(A \,\lor\, C).$$
Comparing, we see $$A = p,\; B = \sim p,\; C = q.$$ Substituting we obtain
$$p \,\lor\, (\sim p \,\land\, q) \;=\; (p \,\lor\, \sim p)\,\land\,(p \,\lor\, q).$$
Now, for any statement $$p$$, the expression $$p \,\lor\, \sim p$$ is always true; it is a tautology. We may therefore replace it by the propositional constant T (True):
$$ (p \,\lor\, \sim p)\,\land\,(p \,\lor\, q) \;=\; \text{T}\,\land\,(p \,\lor\, q).$$
The conjunction of a tautology with any statement leaves that statement unchanged, because T acts like the multiplicative identity in logic. Hence
$$E \;=\; p \,\lor\, q.$$
Having reduced the original expression to $$p \lor q,$$ we now negate it. For this we invoke De Morgan’s law, which states
$$\sim(A \,\lor\, B) \;=\; \sim A \,\land\, \sim B.$$
Applying the law directly with $$A = p$$ and $$B = q,$$ we get
$$\sim E \;=\; \sim(p \,\lor\, q) \;=\; \sim p \,\land\, \sim q.$$
This final form exactly matches Option C in the list.
Hence, the correct answer is Option C.
If the truth value of the statement $$p \to (\sim q \vee r)$$ is false F, then the truth values of the statements p, q, r are respectively
We are told that the compound statement $$p \to (\sim q \vee r)$$ has the truth value False (F).
First, recall the logical rule for an implication. The statement $$A \to B$$ is False only when its antecedent $$A$$ is True and its consequent $$B$$ is False. In every other combination, an implication is True. We now apply this rule to our given implication.
Here, the antecedent is $$p$$ and the consequent is $$(\sim q \vee r)$$. Since the whole implication is False, we must have
$$p = \text{True} \quad\text{and}\quad (\sim q \vee r) = \text{False}.$$
So we have already obtained the first truth value:
$$p = T.$$
Next, we analyze the consequent $$(\sim q \vee r).$$ This is a disjunction (“or”) of two parts, $$\sim q$$ and $$r$$. Remember the truth table for a disjunction. A statement of the form $$X \vee Y$$ is False only when both $$X$$ and $$Y$$ are False:
$$X \vee Y = F \quad\text{iff}\quad X = F \text{ and } Y = F.$$
Applying this rule to $$(\sim q \vee r)$$, the overall disjunction is False, so both pieces must be False:
$$\sim q = F \quad\text{and}\quad r = F.$$
Now we can extract the truth values of $$q$$ and $$r$$ one by one.
Since $$\sim q = F,$$ the negation of $$q$$ is False. A negation is False precisely when the original statement is True. Therefore,
$$q = T.$$
We have already obtained from the disjunction that
$$r = F.$$
Collecting our results, the ordered triple of truth values is
$$\bigl(p,\, q,\, r\bigr) = (T,\, T,\, F).$$
Looking at the options, this matches Option C (labelled “3”).
Hence, the correct answer is Option C.
The contrapositive of the statement "If you are born in India, then you are a citizen of India", is:
We begin by identifying the logical form of the given English statement. The sentence “If you are born in India, then you are a citizen of India” can be written symbolically as $$P \rightarrow Q,$$ where
$$P: \text{You are born in India},$$
$$Q: \text{You are a citizen of India}.$$
Now we recall the definition of a contrapositive. The logical rule states that for any conditional statement $$P \rightarrow Q,$$ the contrapositive is obtained by first negating both the hypothesis and the conclusion, and then reversing their order. In symbols,
$$\text{Contrapositive of } (P \rightarrow Q) \text{ is } (\lnot Q) \rightarrow (\lnot P).$$
So we apply this rule step by step. First, we negate the conclusion $$Q$$:
$$\lnot Q: \text{You are \emph{not} a citizen of India}.$$
Next, we negate the hypothesis $$P$$:
$$\lnot P: \text{You are \emph{not} born in India}.$$
Finally, we place the negated conclusion as the new hypothesis and the negated hypothesis as the new conclusion, giving
$$\lnot Q \rightarrow \lnot P,$$
which translates back into English as “If you are not a citizen of India, then you are not born in India.”
We now compare this derived contrapositive with the options provided:
A. If you are not born in India, then you are not a citizen of India. (Matches $$\lnot P \rightarrow \lnot Q$$, which is the converse of the inverse, not the contrapositive.)
B. If you are a citizen of India, then you are born in India. (This is the converse of the original statement.)
C. If you are born in India, then you are not a citizen of India. (This directly contradicts the original statement.)
D. If you are not a citizen of India, then you are not born in India. (Exactly matches $$\lnot Q \rightarrow \lnot P,$$ the contrapositive.)
We see that option D expresses the correct contrapositive.
Hence, the correct answer is Option D.
The expression $$\sim(\sim p \to q)$$ is logically equivalent to
We begin with the expression $$\sim(\sim p \to q)$$ and shall simplify it carefully, showing every algebraic detail.
First, we recall the implication law:
$$x \to y \;\equiv\; \sim x \;\vee\; y.$$
Here the part playing the role of $$x$$ is $$\sim p$$ and the part playing the role of $$y$$ is $$q$$. Substituting these symbols into the implication law we obtain
$$\bigl(\,\sim p \to q\,\bigr) \;\equiv\; \sim(\,\sim p\,)\;\vee\;q.$$
Now, inside the negation we have a double negation $$\sim(\,\sim p\,)$$, and the rule of double negation states that $$\sim(\,\sim p\,)\equiv p$$. Hence we get
$$\bigl(\,\sim p \to q\,\bigr) \;\equiv\; p \;\vee\; q.$$
Returning to the original expression, we must negate this result. So we write
$$\sim(\,\sim p \to q\,) \;\equiv\; \sim\bigl(p \;\vee\; q\bigr).$$
Next, we invoke De Morgan’s law, which tells us that the negation of a disjunction is the conjunction of the negations:
$$\sim\bigl(p \;\vee\; q\bigr) \;\equiv\; \bigl(\sim p\bigr) \;\wedge\; \bigl(\sim q\bigr).$$
Thus, after carrying out all transformations, the original expression simplifies completely to
$$\sim p \;\wedge\; \sim q.$$
Looking at the options, this matches Option B.
Hence, the correct answer is Option B.
Which one of the following Boolean expression is a tautology?
First, remember that a Boolean expression is called a tautology if it is always true, no matter whether the simple propositions $$p$$ and $$q$$ are true (T) or false (F). To decide which option is a tautology, we shall simplify every given expression algebraically, employing these standard Boolean laws:
$$\begin{aligned} &\text{(1) Distributive law:}&\; a\wedge(b\vee c)= (a\wedge b)\vee(a\wedge c),\\ &\text{(2) Distributive law:}&\; a\vee(b\wedge c)= (a\vee b)\wedge(a\vee c),\\ &\text{(3) Complement law:}&\; a\vee\neg a = \text{T},\; a\wedge\neg a = \text{F},\\ &\text{(4) Identity law:}&\; a\vee\text{F}=a,\; a\wedge\text{T}=a,\\ &\text{(5) Domination law:}&\; a\vee\text{T}=\text{T},\; a\wedge\text{F}= \text{F}. \end{aligned}$$
Now we analyse each option one by one.
Option A: $$ (p \vee q)\wedge (\neg p \vee \neg q) $$
We notice that $$\neg p\vee\neg q$$ is the negation of $$p\wedge q$$ by De Morgan’s law, so we may write
$$ (p\vee q)\wedge\neg(p\wedge q). $$
This is exactly the exclusive-or (“one but not both”) condition. For example, if both $$p$$ and $$q$$ are true, then $$p\wedge q$$ is true, its negation is false, and the whole expression becomes false. Hence Option A is not always true, so it is not a tautology.
Option B: $$ (p\wedge q)\vee(p\wedge\neg q) $$
We factor out the common literal $$p$$ using the distributive law (1):
$$ (p\wedge q)\vee(p\wedge\neg q)= p\wedge (q\vee\neg q). $$
By the complement law (3), $$q\vee\neg q=\text{T}$$, so
$$ p\wedge \text{T}=p. $$
Since $$p$$ can be true or false, the whole expression can also be true or false; therefore it is not a tautology.
Option C: $$ (p\vee q)\wedge(p\vee\neg q) $$
Here we use the distributive law (2) in reverse, pulling out the common literal $$p\vee$$:
$$ (p\vee q)\wedge(p\vee\neg q)= p\vee(q\wedge\neg q). $$
Again by the complement law (3), $$q\wedge\neg q=\text{F}$$, so we get
$$ p\vee \text{F}=p. $$
This reduces to the single variable $$p$$, which is not always true, so Option C is also not a tautology.
Option D: $$ (p \vee q)\vee(\neg p \vee \neg q) $$
Using associativity and commutativity of $$\vee$$, we simply collect all the literals:
$$ (p\vee q)\vee(\neg p\vee \neg q)= p\vee\neg p\vee q\vee\neg q. $$
Now group the complementary pairs:
$$ p\vee\neg p = \text{T}, \quad q\vee\neg q = \text{T}. $$
So the entire expression becomes
$$ \text{T}\vee\text{T}=\text{T}, $$
which is true for every possible truth‐value combination of $$p$$ and $$q$$. Therefore Option D is a tautology.
After examining all four choices, we see that only Option 4 (that is, Option D) is always true.
Hence, the correct answer is Option 4.
Which one of the following statements is not a tautology?
First, recall the definition: a statement (propositional formula) is called a tautology if it evaluates to $$\text{True}$$ for every possible assignment of truth-values to its constituent propositions.
Let us examine each option by constructing its complete truth table. Because we have two simple propositions, $$p$$ and $$q$$, there are exactly four possible ordered pairs $$(p,q)$$, namely $$(T,T),\;(T,F),\;(F,T),\;(F,F).$$ We shall evaluate each compound statement row by row.
Option A is $$\;(p \lor q)\;\rightarrow\;(p \lor \sim q).$$ We compute step by step.
We have
$$\begin{array}{|c|c||c|c||c|} \hline p & q & p\lor q & \sim q & p\lor\sim q \\ \hline T & T & T & F & T \\ \hline T & F & T & T & T \\ \hline F & T & T & F & F \\ \hline F & F & F & T & T \\ \hline \end{array}$$
Now, the implication $$A\rightarrow B$$ is false only when $$A$$ is $$T$$ and $$B$$ is $$F$$. Introducing one extra column for the entire statement, we get
$$\begin{array}{|c|c||c|c|c||c|} \hline p & q & p\lor q & \sim q & p\lor\sim q & (p\lor q)\rightarrow(p\lor\sim q) \\ \hline T & T & T & F & T & T \\ \hline T & F & T & T & T & T \\ \hline F & T & T & F & F & F \\ \hline F & F & F & T & T & T \\ \hline \end{array}$$
Because the third row yields the value $$F$$, the statement is not always true; therefore Option A is not a tautology.
Option B is $$\;(p \land q)\;\rightarrow\;(\sim p \lor q).$$ We proceed similarly:
$$\begin{array}{|c|c||c|c||c|} \hline p & q & p\land q & \sim p & \sim p\lor q \\ \hline T & T & T & F & T \\ \hline T & F & F & F & F \\ \hline F & T & F & T & T \\ \hline F & F & F & T & T \\ \hline \end{array}$$
Adding the implication column,
$$\begin{array}{|c|c||c|c|c||c|} \hline p & q & p\land q & \sim p & \sim p\lor q & (p\land q)\rightarrow(\sim p\lor q) \\ \hline T & T & T & F & T & T \\ \hline T & F & F & F & F & T \\ \hline F & T & F & T & T & T \\ \hline F & F & F & T & T & T \\ \hline \end{array}$$
Every row is $$T$$, so Option B is a tautology.
Option C is $$\;p\;\rightarrow\;(p \lor q).$$ Observe that whenever $$p$$ is $$T$$, the consequent $$p \lor q$$ is automatically $$T$$ (since a disjunction is true if any component is true). Whenever $$p$$ is $$F$$, the implication is vacuously true. Hence every row is $$T$$, confirming that Option C is a tautology.
Option D is $$\;(p \land q)\;\rightarrow\;p.$$ The antecedent can be $$T$$ only when both $$p$$ and $$q$$ are $$T$$, in which case $$p$$ is certainly $$T$$, making the implication true. In all other rows the antecedent is $$F$$, so the implication is again vacuously true. Thus Option D is also a tautology.
Summarising, only Option A fails to remain true under every valuation. It is therefore the single statement that is not a tautology.
Hence, the correct answer is Option A.
If $$p \Rightarrow (q \lor r)$$ is False, then the truth values of p, q, r are respectively, (where T is True and F is False)
First, recall the logical rule for an implication. The statement $$p \Rightarrow s$$ is false only in one specific situation: when the antecedent $$p$$ is True (T) and the consequent $$s$$ is False (F). In every other combination the implication is True. Symbolically, we can rewrite an implication with the formula $$p \Rightarrow s \;=\; \lnot p \,\lor\, s,$$ which confirms the same fact because a disjunction $$\lnot p \lor s$$ fails exactly when $$\lnot p$$ is F (so $$p$$ is T) and simultaneously $$s$$ is F.
Now we apply this rule to the given compound statement $$p \Rightarrow (q \lor r).$$ Here the consequent is the disjunction $$(q \lor r).$$ We are told that the whole implication is False. Therefore, by the rule just stated, the following two conditions must hold together:
1. $$p$$ is True, because the antecedent must be True for the implication to fail.
2. $$(q \lor r)$$ is False, because the consequent must be False for the implication to fail.
Next, we analyse the disjunction $$(q \lor r).$$ A disjunction $$q \lor r$$ is True if at least one of $$q$$ or $$r$$ is True, and it is False only when both $$q$$ and $$r$$ are False. So, for $$(q \lor r)$$ to be False, we must have
$$q = \text{F} \quad \text{and} \quad r = \text{F}.$$
We already found $$p = \text{T}.$$ Putting these results together, the required truth values are
$$p = \text{T}, \qquad q = \text{F}, \qquad r = \text{F}.$$
Looking at the options, this matches Option A, which lists T, F, F in that order.
Hence, the correct answer is Option A.
The negation of the Boolean expression $$\sim s \vee (\sim r \wedge s)$$ is equivalent to
We begin with the Boolean expression whose negation we must find:
$$\sim s \;\vee\; (\sim r \;\wedge\; s).$$
Our objective is to compute its logical negation, that is, to evaluate
$$\sim\bigl(\,\sim s \;\vee\; (\sim r \;\wedge\; s)\bigr).$$
First, we invoke De Morgan’s law for the negation of a disjunction, which states:
$$\sim(A \;\vee\; B) \;=\; (\sim A) \;\wedge\; (\sim B).$$
Here, we identify $$A = \sim s$$ and $$B = (\sim r \;\wedge\; s).$$ Applying the law gives
$$\sim(\,\sim s \;\vee\; (\sim r \;\wedge\; s)) \;=\; \bigl(\sim(\sim s)\bigr) \;\wedge\; \bigl(\sim(\sim r \;\wedge\; s)\bigr).$$
Now, $$\sim(\sim s)$$ is simply $$s,$$ because a double negation cancels itself. Substituting, we have
$$s \;\wedge\; \bigl(\sim(\sim r \;\wedge\; s)\bigr).$$
Next, we must simplify $$\sim(\sim r \;\wedge\; s).$$ We again use De Morgan’s law, this time for the negation of a conjunction:
$$\sim(C \;\wedge\; D) \;=\; (\sim C) \;\vee\; (\sim D).$$
Here, $$C = \sim r$$ and $$D = s.$$ Therefore,
$$\sim(\sim r \;\wedge\; s) \;=\; \bigl(\sim(\sim r)\bigr) \;\vee\; (\sim s).$$
The term $$\sim(\sim r)$$ simplifies to $$r.$$ Hence,
$$\sim(\sim r \;\wedge\; s) \;=\; r \;\vee\; (\sim s).$$
Substituting this back, the overall negation becomes
$$s \;\wedge\; \bigl(r \;\vee\; (\sim s)\bigr).$$
We now distribute $$s$$ over the disjunction $$r \;\vee\; (\sim s).$$ The distributive law of Boolean algebra tells us
$$X \;\wedge\; (Y \;\vee\; Z) \;=\; (X \;\wedge\; Y) \;\vee\; (X \;\wedge\; Z).$$
Taking $$X = s, \; Y = r, \; Z = \sim s,$$ we obtain
$$\bigl(s \;\wedge\; r\bigr) \;\vee\; \bigl(s \;\wedge\; (\sim s)\bigr).$$
The term $$s \;\wedge\; (\sim s)$$ is always false (it equals $$0$$) because a proposition cannot be simultaneously true and false. Hence that term vanishes, leaving
$$s \;\wedge\; r.$$
We have therefore shown that the negation of the original expression simplifies to $$s \wedge r,$$ which is exactly Option 2.
Hence, the correct answer is Option 2.
If q is false and $$p \wedge q \leftrightarrow r$$ is true, then which one of the following statements is a tautology?
We are told that the statement $$q$$ is false and at the same time the biconditional $$(p \wedge q) \leftrightarrow r$$ is true. Let us first interpret this information.
By definition, the conjunction $$p \wedge q$$ is true only when both $$p$$ and $$q$$ are true. Because we already know that $$q$$ is false, the value of the entire conjunction is immediately fixed:
$$p \wedge q = \text{False}.$$
Next, we look at the biconditional. Remember the rule for a biconditional:
For any two statements $$A$$ and $$B$$, the statement $$A \leftrightarrow B$$ is true precisely when either
(i) both $$A$$ and $$B$$ are true, or
(ii) both $$A$$ and $$B$$ are false.
In our problem $$A = (p \wedge q)$$ and $$B = r$$. We have discovered that $$A$$ is false. For the biconditional $$A \leftrightarrow B$$ to be true, case (ii) must hold; therefore $$B$$ must also be false. Concretely,
$$r = \text{False}.$$
At this point we have
$$q = \text{False}, \quad r = \text{False}, \quad p$$ is still free (it can be True or False).
We now inspect each option to see which statement is necessarily true—i.e. a tautology—under these fixed truth values.
Option A: $$(p \vee r) \to (p \wedge r).$$
Because $$r = \text{False},$$ we simplify step by step:
$$p \vee r = p \vee \text{False} = p,$$
$$p \wedge r = p \wedge \text{False} = \text{False}.$$
Thus Option A becomes $$p \to \text{False}.$$ The truth rule for implication says $$A \to B$$ is false exactly when $$A$$ is true and $$B$$ is false. Here, whenever $$p$$ is true the implication is false. Hence Option A is not always true.
Option B: $$(p \wedge r) \to (p \vee r).$$
Again using $$r = \text{False}$$ we get
$$p \wedge r = p \wedge \text{False} = \text{False},$$
$$p \vee r = p \vee \text{False} = p.$$
The whole statement reduces to $$\text{False} \to p.$$ An implication whose antecedent is false is always true, irrespective of the consequent. Therefore Option B is always true for both possibilities of $$p$$ and is thus a tautology.
Option C: $$p \wedge r = p \wedge \text{False} = \text{False}.$$ This is always false, so it certainly is not a tautology.
Option D: $$p \vee r = p \vee \text{False} = p.$$ The truth of this statement depends on whether $$p$$ itself is true or false, so it is not guaranteed to be true in all cases.
Only Option B satisfies the requirement of being always true under the given conditions.
Hence, the correct answer is Option B.
The Boolean expression $$((p \wedge q) \vee (p \vee \sim q)) \wedge (\sim p \wedge \sim q)$$ is equivalent to
We have to simplify the Boolean expression $$\bigl((p \wedge q) \vee (p \vee \sim q)\bigr) \wedge (\sim p \wedge \sim q).$$ Throughout, we shall use the well-known Boolean identities: (i) Absorption Law $$X \vee (X \wedge Y)=X,$$ (ii) Distributive Law $$A \wedge (B \vee C)= (A \wedge B)\; \vee\; (A \wedge C),$$ (iii) Idempotent Law $$Z \wedge Z=Z,$$ and (iv) the fact that any statement conjoined with its negation is false, $$R \wedge (\sim R)=0.$$
First concentrate on the part $$ (p \wedge q) \vee (p \vee \sim q).$$ In order to apply the absorption law, we re-express $$(p \wedge q)$$ in a form that visibly contains $$(p \vee \sim q).$$ Observe that
$$ (p \vee \sim q)\;\wedge\; q \;=\; (p \wedge q)\; \vee\; (\sim q \wedge q).$$
Because $$\sim q \wedge q = 0,$$ the right-hand side reduces to $$p \wedge q.$$ Thus we have shown
$$p \wedge q \;=\; (p \vee \sim q)\;\wedge\; q.$$
Letting $$X = (p \vee \sim q) \quad\text{and}\quad Y = q,$$ we may rewrite the first bracket as $$ (X \wedge Y) \vee X.$$ Now, by the absorption law, $$ (X \wedge Y) \vee X = X.$$ Therefore
$$ (p \wedge q) \vee (p \vee \sim q) = p \vee \sim q.$$
Substituting this back, the whole expression becomes
$$ (p \vee \sim q)\; \wedge\; (\sim p \wedge \sim q).$$
Using associativity and commutativity of $$\wedge,$$ we group as
$$ (\sim p \wedge \sim q)\; \wedge\; (p \vee \sim q).$$
Now apply the distributive law with $$A = (\sim p \wedge \sim q),\; B = p,\; C = \sim q:$$
$$ (\sim p \wedge \sim q \wedge p)\; \vee\; (\sim p \wedge \sim q \wedge \sim q).$$
Simplify each part step by step. In the first term, $$\sim p \wedge p = 0,$$ so
$$\sim p \wedge \sim q \wedge p = 0 \wedge \sim q = 0.$$
In the second term, the idempotent law gives $$\sim q \wedge \sim q = \sim q,$$ therefore
$$\sim p \wedge \sim q \wedge \sim q = \sim p \wedge \sim q.$$
Hence the entire expression reduces to
$$ 0 \;\vee\; (\sim p \wedge \sim q) = \sim p \wedge \sim q.$$
Thus the simplified (and therefore equivalent) Boolean expression is $$ (\sim p) \wedge (\sim q).$$ This matches Option B.
Hence, the correct answer is Option B.
The Boolean expression $$\sim(p \Rightarrow (\sim q))$$ is equivalent to
We have to simplify the Boolean expression $$\sim\!\bigl(p \Rightarrow (\sim q)\bigr)$$ and write the result in one of the listed equivalent forms.
First, we recall the logical equivalence that defines an implication. The implication $$a \Rightarrow b$$ is always equivalent to the disjunction $$(\sim a)\,\vee\, b.$$ We will apply this fact to the inner implication $$p \Rightarrow (\sim q).$$
So we write
$$p \Rightarrow (\sim q) \;=\; (\sim p)\,\vee\,(\sim q).$$
Substituting this back into the original expression gives
$$\sim\!\bigl(p \Rightarrow (\sim q)\bigr) \;=\; \sim\!\bigl((\sim p)\,\vee\,(\sim q)\bigr).$$
Now we must remove the outer negation. For this we make use of De Morgan’s Law, which states:
$$\sim(A \vee B) = (\sim A) \wedge (\sim B), \quad \sim(A \wedge B) = (\sim A) \vee (\sim B).$$
In our case $$A = (\sim p)\quad\text{and}\quad B = (\sim q).$$ Hence
$$\sim\!\bigl((\sim p)\,\vee\,(\sim q)\bigr) = (\sim(\sim p)) \,\wedge\, (\sim(\sim q)).$$
Double negations cancel out, because $$\sim(\sim r)=r$$ for any statement $$r$$. Therefore
$$ (\sim(\sim p)) \,\wedge\, (\sim(\sim q)) = p \,\wedge\, q.$$
Thus we have shown step by step that
$$\sim\!\bigl(p \Rightarrow (\sim q)\bigr) = p \wedge q.$$
The equivalent option in the list is Option D.
Hence, the correct answer is Option D.
If the function $$f: R - \{1, -1\} \rightarrow A$$ defined by $$f(x) = \frac{x^2}{1 - x^2}$$, is surjective, then $$A$$ is equal to:
We are given the function $$f : \mathbb R-\{1,-1\}\to A$$ defined by
$$f(x)=\dfrac{x^{2}}{1-x^{2}}.$$
Our task is to find the set $$A$$ that makes the mapping surjective, that is, every element of $$A$$ must actually be attained as a value of $$f(x)$$ for some admissible $$x$$. So we need the precise range (image) of $$f$$.
First we notice that only the square of $$x$$ appears in the numerator, so it is convenient to set
$$t = x^{2}.$$
This substitution immediately gives two useful facts:
1. Because $$x^{2}\ge 0$$ for all real $$x$$, we have $$t\ge 0.$$
2. The domain restriction $$x\neq \pm1$$ translates to $$t\neq 1.$$ (Indeed, $$x=1$$ or $$x=-1$$ would give $$t=1$$.)
With this change of variable we can rewrite the function as
$$f(x)=\dfrac{t}{1-t},\qquad \text{where}\; t\ge 0,\; t\neq 1.$$
So the problem reduces to finding all real values $$y$$ for which the equation
$$y=\dfrac{t}{1-t}$$
has a solution $$t\ge 0,\,t\neq1.$$ We now study this rational expression carefully.
Case 1: $$0\le t<1$$.
Here the denominator $$1-t$$ is positive, and the numerator $$t$$ is non-negative. Hence
$$y=\dfrac{t}{1-t}\ge 0.$$
We analyse the end-points:
• As $$t\to0^{+}$$ we get $$y\to0.$$
• As $$t\to1^{-}$$ we have $$1-t\to0^{+}$$, so the fraction grows without bound and $$y\to +\infty.$$
Because the function $$t\mapsto\dfrac{t}{1-t}$$ is continuous on $$[0,1)$$, every non-negative real number is attained exactly once. Thus this case contributes the entire interval
$$[0,\infty).$$
Case 2: $$t>1$$.
Now the denominator $$1-t$$ is negative while the numerator $$t$$ is positive. Therefore
$$y=\dfrac{t}{1-t}<0.$$ (A positive number divided by a negative number is negative.)
Again we check limits:
• As $$t\to1^{+}$$ we have $$1-t\to0^{-}$$, so the quotient tends to $$-\infty$$.
• As $$t\to\infty$$ we use the highest-degree terms to estimate $$\dfrac{t}{1-t}=\dfrac{t}{-t\bigl(1-\tfrac1t\bigr)}\approx\dfrac{t}{-t}=-1.$$
To see exactly how it approaches $$-1$$, rearrange the expression algebraically:
$$y=\dfrac{t}{1-t}=-\,\dfrac{t}{t-1}.$$
Since $$\dfrac{t}{t-1}>1$$ for all $$t>1$$, we conclude
$$y<-1.$$
Moreover, the map $$t\mapsto -\dfrac{t}{t-1}$$ is continuous and strictly increasing on $$(1,\infty)$$, so it takes every value from $$-\infty$$ up to (but not including) $$-1$$. Hence this case contributes the interval
$$(-\infty,-1).$$
Combining both cases, we obtain
$$\text{Range}(f)=(-\infty,-1)\,\cup\,[0,\infty).$$
Equivalently, this is the set of all real numbers except those belonging to the open interval $$(-1,0)$$, and we must exclude the single point $$-1$$ itself because it never occurs. Therefore the range can be written succinctly as
$$\mathbb R-\bigl[-1,0\bigr).$$
Among the given options, this set appears exactly as Option C.
Hence, the correct answer is Option C.
Let Z be the set of integers. If $$A = \{x \in Z : 2^{(x+2)(x^2-5x+6)} = 1\}$$ and $$B = \{x \in Z : -3 < 2x - 1 < 9\}$$, then the number of subsets of the set $$A \times B$$, is:
We have the set $$A=\{x\in \mathbb Z:2^{(x+2)\bigl(x^{2}-5x+6\bigr)}=1\}.$$
First, recall the basic fact: for any real number $$k,$$ the equality $$2^{k}=1$$ holds only when $$k=0,$$ because the base $$2$$ is positive and not equal to $$1.$$ Hence, to find all integers $$x$$ belonging to $$A,$$ we must force the exponent to be zero:
$$ (x+2)\bigl(x^{2}-5x+6\bigr)=0. $$
This product equals zero precisely when at least one factor is zero. We split it:
1. $$x+2=0 \;\Longrightarrow\; x=-2.$$
2. $$x^{2}-5x+6=0.$$
We factor the quadratic:
$$ x^{2}-5x+6=(x-2)(x-3). $$
So
$$ (x-2)(x-3)=0 \;\Longrightarrow\; x=2 \text{ or } x=3. $$
Collecting all integer solutions, we obtain
$$ A=\{-2,\,2,\,3\}, $$
which contains $$|A|=3$$ elements.
Now consider the set $$B=\{x\in\mathbb Z:-3<2x-1<9\}.$$ We solve the double inequality step by step.
First, add $$1$$ to every part:
$$ -3+1 < 2x-1+1 < 9+1 \;\Longrightarrow\; -2 < 2x < 10. $$
Next, divide every part by $$2$$ (the sign of $$2$$ is positive, so the inequalities keep their direction):
$$ \frac{-2}{2} < x < \frac{10}{2} \;\Longrightarrow\; -1 < x < 5. $$
The integers strictly between $$-1$$ and $$5$$ are
$$ 0,\;1,\;2,\;3,\;4. $$
Thus
$$ B=\{0,\,1,\,2,\,3,\,4\}, $$
with $$|B|=5$$ elements.
We now form the Cartesian product $$A\times B=\{(a,b):a\in A,\;b\in B\}.$$ The counting principle tells us that
$$ |A\times B|=|A|\times|B|=3\times5=15. $$
Finally, the total number of subsets of any finite set containing $$n$$ elements is given by the formula $$2^{n}.$$ Substituting $$n=15,$$ we get
$$ \text{Number of subsets}=2^{15}. $$
Hence, the correct answer is Option D.
For $$x \in R$$, Let [x] denotes the greatest integer $$\leq x$$, then the sum of the series $$\left[-\frac{1}{3}\right] + \left[-\frac{1}{3} - \frac{1}{100}\right] + \left[-\frac{1}{3} - \frac{2}{100}\right] + \ldots + \left[-\frac{1}{3} - \frac{99}{100}\right]$$ is
We begin by recalling the definition of the greatest-integer (floor) function. By definition, for any real number $$x$$
$$[x]=n \quad\text{if and only if}\quad n\le x<n+1,$$
where $$n$$ is an integer. In words, $$[x]$$ is the largest integer that is not greater than $$x$$.
The series to be summed is
$$\left[-\frac13\right]+\left[-\frac13-\frac1{100}\right]+\left[-\frac13-\frac2{100}\right]+\ldots+\left[-\frac13-\frac{99}{100}\right].$$
To handle all the terms uniformly, let us label the general (k-th) term:
$$T_k=\left[-\frac13-\frac{k}{100}\right], \qquad k=0,1,2,\ldots ,99.$$
Our task is to find $$T_k$$ for every integer $$k$$ in the stated range and then add all the $$T_k$$.
First, convert $$\displaystyle -\frac13$$ into its decimal form for easy comparison:
$$-\frac13=-0.333333\ldots$$
Next, observe that
$$-\frac13-\frac{k}{100}=-0.333333\ldots-\frac{k}{100}.$$
Because $$\dfrac{k}{100}$$ varies from $$0$$ (when $$k=0$$) to $$\dfrac{99}{100}=0.99$$ (when $$k=99$$), the expression
$$\alpha_k=-\frac13-\frac{k}{100}$$
will move from
$$\alpha_0=-0.333333\ldots$$
down to
$$\alpha_{99}=-0.333333\ldots-0.99=-1.323333\ldots$$
Thus each $$\alpha_k$$ lies in the interval
$$-1.323333\ldots\le\alpha_k\le-0.333333\ldots$$
Within this interval the only integers that can serve as greatest integers are $$-1$$ and $$-2$$, because
$$-2<-1.323333\ldots\le\alpha_k\le-0.333333\ldots<0.$$
So every term $$T_k$$ equals either $$-1$$ or $$-2$$. To decide which, locate the point where $$\alpha_k$$ crosses $$-1$$. We need
$$\alpha_k<-1\quad\Longleftrightarrow\quad -\frac13-\frac{k}{100}<-1.$$
Rearranging, add $$\dfrac13$$ to both sides:
$$-\frac{k}{100}<-1+\frac13=-\frac23.$$
Multiplying by $$-1$$ reverses the inequality:
$$\frac{k}{100}>\frac23.$$
Now convert $$\dfrac23$$ to a decimal:
$$\frac23=0.666666\ldots$$
Hence
$$\frac{k}{100}>0.666666\ldots\quad\Longleftrightarrow\quad k>66.6666\ldots$$
Since $$k$$ is an integer, the inequality becomes
$$k\ge 67.$$
We have therefore obtained two cases.
• If $$0\le k\le 66$$, then $$\alpha_k\ge-1$$, so
$$T_k=[\alpha_k]=-1.$$
• If $$67\le k\le 99$$, then $$\alpha_k<-1$$, but always $$\alpha_k>-2$$, so
$$T_k=[\alpha_k]=-2.$$
Count how many times each value occurs.
• For $$k=0,1,2,\ldots,66$$ we have $$67$$ integers, giving $$67$$ occurrences of $$-1$$.
• For $$k=67,68,\ldots,99$$ we have $$99-67+1=33$$ integers, giving $$33$$ occurrences of $$-2$$.
Now add all the terms:
$$\text{Sum}=67(-1)+33(-2).$$
Simplify step by step:
$$67(-1)=-67,$$
$$33(-2)=-66,$$
and finally
$$-67-66=-133.$$
Hence, the correct answer is Option D.
Let a function $$f : (0, \infty) \to (0, \infty)$$ be defined by $$f(x) = \left|1 - \frac{1}{x}\right|$$. Then f is:
First remember the definition of a function: every element of the domain must be assigned an image that actually lies inside the codomain. The codomain fixed by the question is $$(0,\infty),$$ i.e. the set of strictly positive real numbers.
Now we examine the value of the given rule at the point $$x=1.$$ Substituting in the formula
$$f(x)=\left|1-\frac1x\right|,$$
we obtain
$$f(1)=\left|1-\frac11\right|=\left|1-1\right|=\left|0\right|=0.$$
But $$0\notin(0,\infty).$$ Therefore the image of the point $$x=1$$ does not belong to the declared codomain. This violates the very definition of a function from $$(0,\infty)$$ to $$(0,\infty).$$
Because the mapping is not even well-defined with the announced codomain, questions about injectivity or surjectivity are meaningless: the object under discussion fails to be a bona-fide function in the first place. Consequently none of the descriptions “injective only”, “not injective but surjective”, or “neither injective nor surjective” can be accepted.
Hence, the correct answer is Option D.
Let $$f(x) = x^2$$, $$x \in R$$. For any $$A \subseteq R$$, define $$g(A) = \{x \in R : f(x) \in A\}$$. If $$S = [0, 4]$$, then which one of the following statements is not true?
We have the function $$f(x)=x^{2}$$ defined for every real number $$x$$.
For any subset $$A\subseteq \mathbb R$$, we are told to define
$$g(A)=\{x\in\mathbb R: f(x)\in A\}.$$
This means $$g(A)$$ is the set of all real numbers whose squares belong to the set $$A$$; in other words, $$g(A)$$ is the pre-image of $$A$$ under the squaring function.
Now let us fix the set $$S=[0,4].$$ We shall compute the four quantities that occur in the options one by one.
First we find $$f(S).$$
Every number in $$S$$ satisfies $$0\le x\le 4$$. Squaring preserves order for non-negative numbers, so
$$0^{2}\le x^{2}\le 4^{2}\quad\Longrightarrow\quad 0\le x^{2}\le16.$$
Hence
$$f(S)=\{x^{2}:x\in[0,4]\}=[0,16].$$
Next we find $$g(S).$$
By definition,
$$g(S)=\{x\in\mathbb R:f(x)\in S\}=\{x\in\mathbb R:x^{2}\in[0,4]\}.$$
The condition $$x^{2}\in[0,4]$$ means
$$0\le x^{2}\le4.$$
Taking square roots gives $$|x|\le2,$$ which is equivalent to
$$-2\le x\le2.$$
Therefore
$$g(S)=[-2,2].$$
Now we compute $$f(g(S)).$$
We already know $$g(S)=[-2,2].$$ Applying $$f(x)=x^{2}$$ to every number in this interval, we obtain
$$f(g(S))=\{x^{2}:x\in[-2,2]\}.$$
The smallest value of $$x^{2}$$ on $$[-2,2]$$ is $$0^{2}=0,$$ and the largest value is $$2^{2}=4.$$ Hence
$$f(g(S))=[0,4].$$
Observe that $$[0,4]=S,$$ so
$$f(g(S))=S.$$
Next we compute $$g(f(S)).$$
We already showed $$f(S)=[0,16].$$ By definition,
$$g(f(S))=\{x\in\mathbb R:x^{2}\in[0,16]\}.$$
The condition $$x^{2}\le16$$ is equivalent to $$|x|\le4,$$ that is
$$-4\le x\le4.$$
Hence
$$g(f(S))=[-4,4].$$
Finally we compare the sets obtained so far.
We have
$$S=[0,4],\qquad f(S)=[0,16],\qquad g(S)=[-2,2],\qquad f(g(S))=[0,4],\qquad g(f(S))=[-4,4].$$
Let us examine each option.
Option A states $$g(f(S))\neq S.$$ Since $$g(f(S))=[-4,4]$$ and $$S=[0,4],$$ the two intervals differ (for example, $$-2\in[-4,4]$$ but $$-2\notin[0,4]$$). Therefore the inequality is correct; Option A is a true statement.
Option B states $$f(g(S))\neq f(S).$$ We found $$f(g(S))=[0,4]$$ whereas $$f(S)=[0,16]$$, so they are indeed unequal. Thus Option B is also true.
Option C asserts $$f(g(S))=S.$$ We have already proved $$f(g(S))=[0,4]=S,$$ so Option C is true.
Option D asserts $$g(f(S))=g(S).$$ But $$g(f(S))=[-4,4]$$ while $$g(S)=[-2,2];$$ these two sets are not equal because, for instance, $$3\in[-4,4]$$ but $$3\notin[-2,2].$$ Hence Option D is false.
Because the question asks for the statement that is not true, we conclude that Option D is the required choice.
Hence, the correct answer is Option D.
Let $$N$$ be the set of natural numbers and two functions $$f$$ and $$g$$ be defined as $$f, g: N \to N$$ such that $$f(n) = \begin{cases} \frac{n+1}{2}, & \text{if n is odd} \\ \frac{n}{2}, & \text{if n is even} \end{cases}$$ and $$g(n) = n - (-1)^n$$. Then $$fog$$ is:
We consider the set of natural numbers $$N=\{1,2,3,\dots\}$$ and the two given functions
$$f:N\to N,\qquad f(n)= \begin{cases} \dfrac{n+1}{2}, & \text{if }n\text{ is odd}\\[6pt] \dfrac{n}{2}, & \text{if }n\text{ is even} \end{cases}$$
and
$$g:N\to N,\qquad g(n)=n-(-1)^n.$$
First we rewrite $$g$$ separately for even and odd inputs. We know the elementary fact $$(-1)^n=\begin{cases}1,& n\text{ even}\\-1,& n\text{ odd.}\end{cases}$$ Using this fact, we have
For even $$n,$$ say $$n=2k,$$
$$g(2k)=2k-1.$$
For odd $$n,$$ say $$n=2k-1,$$
$$g(2k-1)=2k-1-(-1)^{2k-1}=2k-1-(-1)=2k.$$
So
$$g(n)=\begin{cases} n-1,& n \text{ even}\\ n+1,& n \text{ odd}. \end{cases}$$
Now we evaluate the composition $$f\circ g,$$ that is, $$\bigl(f\circ g\bigr)(n)=f\bigl(g(n)\bigr).$$ We again consider the parity of $$n.$$
Case 1 : $$n$$ is even. Write $$n=2k.$$ Then
$$g(n)=g(2k)=2k-1,$$
and this number $$2k-1$$ is odd. When the input to $$f$$ is odd we use the first branch of $$f,$$ hence
$$f\bigl(g(2k)\bigr)=f(2k-1)=\dfrac{(2k-1)+1}{2}=\dfrac{2k}{2}=k.$$
Because $$n=2k,$$ we can rewrite this result as
$$\bigl(f\circ g\bigr)(n)=\dfrac{n}{2},\qquad n\text{ even}.$$
Case 2 : $$n$$ is odd. Write $$n=2k-1.$$ Then
$$g(n)=g(2k-1)=2k,$$
and this output $$2k$$ is even. For an even input, $$f$$ takes its second branch, giving
$$f\bigl(g(2k-1)\bigr)=f(2k)=\dfrac{2k}{2}=k.$$
Because $$n=2k-1,$$ this can be rewritten as
$$\bigl(f\circ g\bigr)(n)=\dfrac{n+1}{2},\qquad n\text{ odd}.$$
Combining the two cases, we obtain the explicit expression
$$\boxed{\bigl(f\circ g\bigr)(n)= \begin{cases} \dfrac{n+1}{2}, & n\text{ odd}\\[6pt] \dfrac{n}{2}, & n\text{ even} \end{cases}}$$
We notice that this is exactly the same rule that defines $$f$$ itself. Hence $$f\circ g=f.$$ To decide between the options we must examine whether this function is one-one (injective) and/or onto (surjective) as a map from $$N$$ to $$N.$$
Injectivity test. We compute two different inputs that yield the same output:
$$f(1)=\dfrac{1+1}{2}=1,\qquad f(2)=\dfrac{2}{2}=1.$$
The values $$1$$ and $$2$$ are distinct, yet $$f(1)=f(2).$$ Therefore $$f$$ is not one-one. Since $$f\circ g=f,$$ the composition is also not one-one.
Surjectivity test. Take any arbitrary natural number $$m\in N.$$ Choosing $$n=2m$$ (which is even) gives
$$f(2m)=\dfrac{2m}{2}=m.$$
Thus every element $$m$$ in the codomain $$N$$ is hit by some element of the domain, so $$f$$ is onto, and therefore $$f\circ g$$ is also onto.
We have proved that $$f\circ g$$ is onto but not one-one.
Hence, the correct answer is Option A.
For $$x \in R - \{0, 1\}$$, let $$f_1(x) = \frac{1}{x}$$, $$f_2(x) = 1 - x$$ and $$f_3(x) = \frac{1}{1-x}$$ be three given functions. If a function, $$J(x)$$ satisfies $$(f_2 \circ J \circ f_1)(x) = f_3(x)$$ then $$J(x)$$ is equal to:
We have three given functions defined for all real numbers with $$x \neq 0,\,1$$:
$$f_1(x)=\dfrac{1}{x}, \qquad f_2(x)=1-x, \qquad f_3(x)=\dfrac{1}{1-x}.$$
According to the statement, the function $$J(x)$$ must satisfy
$$(f_2 \circ J \circ f_1)(x)=f_3(x).$$
The symbol “$$\circ$$” denotes composition, so
$$(f_2 \circ J \circ f_1)(x)=f_2\bigl(J(f_1(x))\bigr).$$
Substituting the explicit expression of $$f_1(x)$$, we get
$$f_2\!\left(J\!\left(\dfrac{1}{x}\right)\right)=f_3(x).$$
Next, we write down the formulas that will be used:
• For every real number $$z$$ (with the necessary domain restrictions) we have $$f_2(z)=1-z.$$
• By definition, $$f_3(x)=\dfrac{1}{1-x}.$$
Applying the first formula with $$z=J\!\left(\dfrac{1}{x}\right)$$ we obtain
$$1-J\!\left(\dfrac{1}{x}\right)=\dfrac{1}{1-x}.$$
Now we isolate the expression containing $$J$$ by transposing terms:
$$J\!\left(\dfrac{1}{x}\right)=1-\dfrac{1}{1-x}.$$
To remove the complex fraction, we combine the terms on the right-hand side. First, we rewrite the rightmost fraction with a common denominator:
$$1=\dfrac{1-x}{1-x},$$
so
$$1-\dfrac{1}{1-x}=\dfrac{1-x}{1-x}-\dfrac{1}{1-x}=\dfrac{1-x-1}{1-x}=\dfrac{-x}{1-x}.$$
In the numerator we factor out $$-1$$ and simultaneously switch the order in the denominator to keep the overall value unchanged:
$$\dfrac{-x}{1-x}=\dfrac{x}{x-1}.$$
Thus we have obtained
$$J\!\left(\dfrac{1}{x}\right)=\dfrac{x}{x-1}.$$
To rewrite the result directly in terms of the input variable of $$J,$$ let us set
$$t=\dfrac{1}{x}\quad\Longrightarrow\quad x=\dfrac{1}{t}.$$
Replacing every occurrence of $$x$$ by $$1/t$$ in the last equation yields
$$J(t)=\dfrac{\dfrac{1}{t}}{\dfrac{1}{t}-1}.$$
We simplify this fraction step by step. The numerator is $$1/t$$. The denominator simplifies as follows:
$$\dfrac{1}{t}-1=\dfrac{1-t}{t}.$$
Hence,
$$J(t)=\frac{\dfrac{1}{t}}{\dfrac{1-t}{t}}.$$
Dividing one fraction by another is equivalent to multiplying by the reciprocal of the denominator, so
$$J(t)=\dfrac{1}{t}\times\dfrac{t}{1-t}=\dfrac{1}{1-t}.$$
But the right-hand side is precisely the definition of $$f_3(t).$$ Therefore, for every allowed value of $$t,$$
$$J(t)=f_3(t).$$
Removing the dummy variable $$t$$ and returning to the standard notation, we conclude
$$J(x)=f_3(x).$$
Hence, the correct answer is Option A.
Let $$f : R \to R$$ be defined by $$f(x) = \frac{x}{1+x^2}$$, $$x \in R$$. Then the range of $$f$$ is
We have a real-valued function $$f:\mathbb R \to \mathbb R$$ defined by
$$f(x)=\dfrac{x}{1+x^{2}}, \qquad x\in\mathbb R.$$
To determine the range of $$f$$ we need all possible values taken by $$\dfrac{x}{1+x^{2}}$$ as $$x$$ varies over every real number.
Because the expression is a quotient of differentiable functions and the denominator $$1+x^{2}$$ is never zero, $$f(x)$$ is continuous for every real $$x$$. For a continuous function on the entire real line, extreme values (if any) will occur either at critical points (where the derivative is zero or undefined) or as $$x\to\pm\infty$$.
First we compute the derivative. We state the Quotient Rule: if $$g(x)=\dfrac{u(x)}{v(x)}$$ with both $$u, v$$ differentiable and $$v(x)\neq0$$, then
$$g'(x)=\dfrac{u'(x)v(x)-u(x)v'(x)}{[v(x)]^{2}}.$$
Here $$u(x)=x$$ and $$v(x)=1+x^{2}$$. Their derivatives are $$u'(x)=1$$ and $$v'(x)=2x$$. Substituting into the Quotient Rule we obtain
$$f'(x)=\dfrac{1\cdot(1+x^{2})-x\cdot(2x)}{(1+x^{2})^{2}} =\dfrac{1+x^{2}-2x^{2}}{(1+x^{2})^{2}} =\dfrac{1-x^{2}}{(1+x^{2})^{2}}.$$
A critical point occurs where $$f'(x)=0$$ or $$f'(x)$$ is undefined. The denominator $$\bigl(1+x^{2}\bigr)^{2}$$ is always positive, so the only way $$f'(x)=0$$ is when the numerator $$1-x^{2}=0$$. Solving,
$$1-x^{2}=0 \;\Longrightarrow\; x^{2}=1 \;\Longrightarrow\; x=\pm1.$$
Thus, the critical points are $$x=1$$ and $$x=-1$$. We now evaluate $$f(x)$$ at these points:
For $$x=1$$:
$$f(1)=\dfrac{1}{1+1^{2}}=\dfrac{1}{2}.$$
For $$x=-1$$:
$$f(-1)=\dfrac{-1}{1+(-1)^{2}}=\dfrac{-1}{2}.$$
Next, we study the behaviour of $$f(x)$$ as $$x$$ tends to infinity or minus infinity. We write
$$\lim_{x\to\infty}f(x)=\lim_{x\to\infty}\dfrac{x}{1+x^{2}} =\lim_{x\to\infty}\dfrac{1/x}{1/x^{2}+1} =\dfrac{0}{0+1}=0.$$
Similarly,
$$\lim_{x\to-\infty}f(x)=0.$$
So the function approaches $$0$$ from both sides but never exceeds (in magnitude) the values found at the critical points. To confirm that $$\dfrac{1}{2}$$ is the greatest and $$-\dfrac{1}{2}$$ is the least value, we examine the sign of the derivative.
Using $$f'(x)=\dfrac{1-x^{2}}{(1+x^{2})^{2}}$$, notice
- When $$|x|<1$$, the numerator $$1-x^{2}>0$$, so $$f'(x)>0$$ and the function is increasing.
- When $$|x|>1$$, the numerator $$1-x^{2}<0$$, so $$f'(x)<0$$ and the function is decreasing.
Hence $$x=1$$ gives a local maximum value $$\dfrac{1}{2}$$, and $$x=-1$$ gives a local minimum value $$-\dfrac{1}{2}$$. There are no larger or smaller values because the function decreases as we move away from these points and approaches $$0$$ asymptotically.
Therefore the set of all values attained by $$f(x)$$ is the closed interval
$$\left[-\dfrac{1}{2},\,\dfrac{1}{2}\right].$$
So the range is exactly $$\left[-\dfrac{1}{2},\,\dfrac{1}{2}\right]$$, which corresponds to Option A.
Hence, the correct answer is Option A.
Let $$f(x) = a^x$$ ($$a > 0$$) be written as $$f(x) = f_1(x) + f_2(x)$$, where $$f_1(x)$$ is an even function and $$f_2(x)$$ is an odd function. Then $$f_1(x + y) + f_1(x - y)$$ equals:
We start with the given exponential function $$f(x)=a^{\,x}$$ where $$a>0$$.
Every real-valued function can be split uniquely into an even part and an odd part. The standard identities are
$$ f_1(x)=\frac{f(x)+f(-x)}{2}\qquad\text{(even part)},\qquad f_2(x)=\frac{f(x)-f(-x)}{2}\qquad\text{(odd part)}. $$
Substituting $$f(x)=a^{\,x}$$, we obtain
$$ f_1(x)=\frac{a^{\,x}+a^{-x}}{2},\qquad f_2(x)=\frac{a^{\,x}-a^{-x}}{2}. $$
Now we compute $$f_1(x+y)$$:
$$ f_1(x+y)=\frac{a^{\,x+y}+a^{-(x+y)}}{2} =\frac{a^{\,x+y}+a^{-x-y}}{2}. $$
Next, we compute $$f_1(x-y)$$:
$$ f_1(x-y)=\frac{a^{\,x-y}+a^{-(x-y)}}{2} =\frac{a^{\,x-y}+a^{-x+y}}{2}. $$
Adding these two expressions term-by-term gives
$$ f_1(x+y)+f_1(x-y) =\frac{a^{\,x+y}+a^{-x-y}+a^{\,x-y}+a^{-x+y}}{2}. $$
To see the desired pattern, we now form $$2f_1(x)f_1(y)$$. First compute the individual factors:
$$ f_1(x)=\frac{a^{\,x}+a^{-x}}{2},\qquad f_1(y)=\frac{a^{\,y}+a^{-y}}{2}. $$
Multiplying these and then doubling gives
$$ 2f_1(x)f_1(y) =2\left(\frac{a^{\,x}+a^{-x}}{2}\right)\left(\frac{a^{\,y}+a^{-y}}{2}\right) =\frac{(a^{\,x}+a^{-x})(a^{\,y}+a^{-y})}{2}. $$
Expanding the product in the numerator, we have
$$ (a^{\,x}+a^{-x})(a^{\,y}+a^{-y}) =a^{\,x+y}+a^{\,x-y}+a^{-x+y}+a^{-x-y}. $$
Therefore
$$ 2f_1(x)f_1(y) =\frac{a^{\,x+y}+a^{\,x-y}+a^{-x+y}+a^{-x-y}}{2}. $$
Comparing this expression with the earlier result for $$f_1(x+y)+f_1(x-y)$$, we see they are identical:
$$ f_1(x+y)+f_1(x-y)=2f_1(x)f_1(y). $$
Hence, the correct answer is Option A.
The domain of the definition of the function $$f(x) = \frac{1}{4 - x^2} + \log_{10}(x^3 - x)$$ is:
We have to find all real numbers $$x$$ for which the two separate parts of the given expression
$$f(x)=\dfrac{1}{4-x^{2}}+\log_{10}\!\bigl(x^{3}-x\bigr)$$
are simultaneously well-defined.
For the rational term $$\dfrac{1}{4-x^{2}}$$ the denominator must never be zero. We write
$$4-x^{2}\neq 0$$
$$\iff\;-x^{2}\neq -4$$
$$\iff\;x^{2}\neq 4$$
$$\iff\;x\neq \pm 2.$$
There is no further restriction here because a non-zero denominator may be positive or negative; we only exclude the points where it vanishes, namely $$x=-2$$ and $$x=2.$$
For the logarithmic term $$\log_{10}\!\bigl(x^{3}-x\bigr)$$ the argument of the logarithm must be strictly positive. Recalling the basic rule
“A real logarithm $$\log_{a}(y)$$ is defined only when $$y>0,$$”
we impose
$$x^{3}-x>0.$$
We factor the cubic completely:
$$x^{3}-x = x\bigl(x^{2}-1\bigr)$$
$$=x(x-1)(x+1).$$
So we need
$$x(x-1)(x+1)>0.$$
To solve this inequality we examine the sign of the product across the critical points $$x=-1,\;0,\;1.$$ We set up intervals and test each one.
1. Interval $$(-\infty,-1):$$ choose $$x=-2.$$
$$(-2)(-2-1)(-2+1)=(-2)(-3)(-1)=6\cdot(-1)=-6<0.$$
2. Interval $$(-1,0):$$ choose $$x=-\tfrac12.$$
$$\Bigl(-\tfrac12\Bigr)\Bigl(-\tfrac12-1\Bigr)\Bigl(-\tfrac12+1\Bigr) =\Bigl(-\tfrac12\Bigr)\Bigl(-\tfrac32\Bigr)\Bigl(\tfrac12\Bigr) =\tfrac34\cdot\tfrac12=\tfrac38>0.$$
3. Interval $$(0,1):$$ choose $$x=\tfrac12.$$
$$\Bigl(\tfrac12\Bigr)\Bigl(\tfrac12-1\Bigr)\Bigl(\tfrac12+1\Bigr) =\Bigl(\tfrac12\Bigr)\Bigl(-\tfrac12\Bigr)\Bigl(\tfrac32\Bigr) =-\tfrac14\cdot\tfrac32=-\tfrac38<0.$$
4. Interval $$(1,\infty):$$ choose $$x=2.$$
$$(2)(2-1)(2+1)=2\cdot1\cdot3=6>0.$$
The product is therefore positive on
$$(-1,0)\quad\text{and}\quad(1,\infty).$$
Combining both sets of conditions:
- From the logarithm: $$x\in(-1,0)\cup(1,\infty).$$
- From the denominator: $$x\neq -2,\;2.$$ The point $$-2$$ is already outside the first set, but $$2$$ lies inside $$(1,\infty)$$ and must be removed.
Subtracting the single forbidden point $$x=2$$ from $$(1,\infty)$$ splits that interval into two pieces:
$$(1,\infty)\setminus\{2\}=(1,2)\cup(2,\infty).$$
Putting everything together, the set of all admissible $$x$$ is
$$(-1,0)\;\cup\;(1,2)\;\cup\;(2,\infty).$$
This collection exactly matches Option A.
Hence, the correct answer is Option A.
Let $$A = \{x \in R : x$$ is not a positive integer$$\}$$. Define a function $$f: A \to R$$ as $$f(x) = \frac{2x}{x-1}$$, then $$f$$ is:
Let $$S = \{x \in R : x \geq 0$$ & $$2|\sqrt{x} - 3| + \sqrt{x}(\sqrt{x} - 6) + 6 = 0\}$$. Then S:
We begin by observing that the unknown appears inside a square-root, so it is convenient to set $$t=\sqrt{x}\,.$$
Because $$x\ge 0,$$ we automatically have $$t\ge 0.$$ With this substitution the given condition
$$2\lvert\sqrt{x}-3\rvert+\sqrt{x}\,(\sqrt{x}-6)+6=0$$
becomes a purely quadratic-absolute value equation in $$t$$:
$$2\lvert t-3\rvert+t(t-6)+6=0.$$
Simplifying the second term first, we write
$$t(t-6)=t^{2}-6t.$$
Hence the complete equation is
$$2\lvert t-3\rvert+t^{2}-6t+6=0. \quad -(1)$$
The absolute value necessitates splitting into two cases.
Case 1: $$t\ge 3$$. Here $$\lvert t-3\rvert=t-3.$$ Substituting into (1) we get
$$2(t-3)+t^{2}-6t+6=0.$$
Expanding the brackets,
$$2t-6+t^{2}-6t+6=0.$$
Combining like terms,
$$t^{2}-4t=0.$$
Factoring,
$$t(t-4)=0.$$
This quadratic yields two possible roots:
$$t=0\quad\text{or}\quad t=4.$$
However, in the present case we imposed $$t\ge 3,$$ so only $$t=4$$ survives. Translating back,
$$x=t^{2}=4^{2}=16.$$
Case 2: $$0\le t<3$$. Here $$\lvert t-3\rvert=3-t.$$ Substituting into (1) we have
$$2(3-t)+t^{2}-6t+6=0.$$
Expanding,
$$6-2t+t^{2}-6t+6=0.$$
Combining constants and like terms,
$$t^{2}-8t+12=0.$$
To solve the quadratic, we use the standard formula $$t=\dfrac{-b\pm\sqrt{b^{2}-4ac}}{2a}$$ with $$a=1,\;b=-8,\;c=12.$$ This gives
$$t=\dfrac{8\pm\sqrt{64-48}}{2}=\dfrac{8\pm\sqrt{16}}{2}=\dfrac{8\pm4}{2}.$$ So,
$$t=6\quad\text{or}\quad t=2.$$
But the current case demands $$t<3,$$ hence only $$t=2$$ is admissible. Converting back to $$x$$ gives
$$x=t^{2}=2^{2}=4.$$
Combining both cases, the set $$S$$ is
$$S=\{4,\;16\}.$$
This set clearly has exactly two distinct non-negative elements.
Hence, the correct answer is Option D.
Let N denote the set of all natural numbers. Define two binary relations on N as $$R_1 = \{(x, y) \in N \times N : 2x + y = 10\}$$ and $$R_2 = \{(x, y) \in N \times N : x + 2y = 10\}$$. Then:
We have two relations on the set of natural numbers $$N$$.
The first relation is defined by $$R_1=\{(x,y)\in N\times N:2x+y=10\}$$. To list all ordered pairs of natural numbers that satisfy $$2x+y=10$$ we solve for every admissible integer value of $$x$$.
Let $$x=1\;(\text{natural}),\;2\cdot1+y=10\Rightarrow y=10-2=8.$$ Let $$x=2,\;2\cdot2+y=10\Rightarrow y=10-4=6.$$ Let $$x=3,\;2\cdot3+y=10\Rightarrow y=10-6=4.$$ Let $$x=4,\;2\cdot4+y=10\Rightarrow y=10-8=2.$$ Let $$x=5,\;2\cdot5+y=10\Rightarrow y=10-10=0,$$ which is not a positive natural number, so we stop here. Thus $$R_1=\{(1,8),\,(2,6),\,(3,4),\,(4,2)\}.$
The range of a relation is the set of all second components. Hence $$\text{Range}(R_1)=\{8,6,4,2\}=\{2,4,6,8\}.$$ Option C claims the range is $$\{2,4,8\},$$ which omits $$6,$$ so that statement is false.
Now consider symmetry for $$R_1$$. A relation is symmetric if $$\forall\,(x,y)\in R,\;(y,x)\in R.$$ Because $$(1,8)\in R_1$$ yet $$(8,1)\notin R_1$$ (since $$2\cdot8+1=17\neq10$$), $$R_1$$ is not symmetric. To test transitivity we recall: a relation is transitive if $$(x,y)\in R\;\text{and}\;(y,z)\in R\implies(x,z)\in R.$$ Take the pairs $$(4,2)\in R_1$$ and $$(2,6)\in R_1.$$ Their “middle” element is $$2,$$ so we must check whether $$(4,6)\in R_1.$$ But $$2\cdot4+6=14\neq10,$$ so $$(4,6)\notin R_1.$$ Hence $$R_1$$ is not transitive either.
The second relation is $$R_2=\{(x,y)\in N\times N:x+2y=10\}.$
Again we enumerate:
Let $$y=1,\;x+2\cdot1=10\Rightarrow x=10-2=8.$$ Let $$y=2,\;x+4=10\Rightarrow x=6.$$ Let $$y=3,\;x+6=10\Rightarrow x=4.$$ Let $$y=4,\;x+8=10\Rightarrow x=2.$$ Let $$y=5,\;x+10=10\Rightarrow x=0,$$ not a positive natural number, so we stop. Thus $$R_2=\{(8,1),\,(6,2),\,(4,3),\,(2,4)\}.$$
The range is the set of all second components, so $$\text{Range}(R_2)=\{1,2,3,4\}.$$ This matches exactly what Option B states.
For symmetry of $$R_2$$, observe $$(8,1)\in R_2$$ but $$(1,8)\notin R_2$$ because $$1+2\cdot8=17\neq10.$$ Hence $$R_2$$ is not symmetric.
For transitivity of $$R_2$$ we again use the definition. Take $$(6,2)\in R_2$$ and $$(2,4)\in R_2.$$ Because they chain through the element $$2,$$ we test $$(6,4).$$ Compute $$6+2\cdot4=14\neq10,$$ so $$(6,4)\notin R_2.$$ Thus $$R_2$$ is not transitive.
Summarising our findings:
• Neither relation is symmetric, so Option D is false. • Neither relation is transitive, so Option A is false. • The range of $$R_1$$ is $$\{2,4,6,8\},$$ not $$\{2,4,8\},$$ so Option C is false. • The range of $$R_2$$ is indeed $$\{1,2,3,4\},$$ so Option B is correct.
Hence, the correct answer is Option B.
Let $$f : A \to B$$ be a function defined as $$f(x) = \frac{x-1}{x-2}$$, where $$A = R - \{2\}$$ and $$B = R - \{1\}$$. Then f is:
We are given the function $$f : A \to B$$ with the definition $$f(x)=\dfrac{x-1}{x-2}$$, where the domain is $$A=\mathbb R-\{2\}$$ and the codomain is $$B=\mathbb R-\{1\}$$. Our task is to decide whether the function is invertible and, if it is, to compute its inverse explicitly.
First, we check injectivity. We take two arbitrary points $$x_1, x_2\in A$$ and assume $$f(x_1)=f(x_2)$$. That equality means
$$\dfrac{x_1-1}{x_1-2}=\dfrac{x_2-1}{x_2-2}.$$
Because both denominators are non-zero (each $$x_i\neq2$$), we cross-multiply:
$$ (x_1-1)(x_2-2)=(x_2-1)(x_1-2). $$
We expand each side completely:
$$ x_1x_2-2x_1-x_2+2 = x_1x_2-2x_2-x_1+2. $$
Now we cancel the common term $$x_1x_2$$ on both sides and gather the remaining terms. Subtract the right side from the left side:
$$ (-2x_1 - x_2 + 2) - (-2x_2 - x_1 + 2)=0. $$
Simplifying the expression inside the brackets, we get
$$ -2x_1 - x_2 + 2 + 2x_2 + x_1 - 2 = 0. $$
The constants $$+2$$ and $$-2$$ cancel, leaving
$$ -2x_1 - x_2 + 2x_2 + x_1 = 0. $$
Combining like terms, we have
$$ (-2x_1 + x_1) + (-x_2 + 2x_2) = 0, $$
which is
$$ -x_1 + x_2 = 0. $$
Thus $$x_2 = x_1$$. Because the only way $$f(x_1) = f(x_2)$$ occurs is when the two inputs are identical, the function is injective.
Next, we verify surjectivity onto $$B$$. Let an arbitrary $$y \in B$$ be given. We must find an $$x \in A$$ satisfying $$f(x)=y$$, that is,
$$ y = \dfrac{x-1}{x-2}. $$
We now solve this equation for $$x$$. First we write the relation in the equivalent cross-multiplied form:
$$ y(x-2)=x-1. $$
Expanding the left side gives
$$ yx-2y = x-1. $$
We want to gather all terms containing $$x$$ on one side, so we subtract $$x$$ from both sides:
$$ yx - x - 2y = -1. $$
We factor out $$x$$ from the two terms containing it, using the distributive law $$ax+bx=(a+b)x$$:
$$ x(y-1) - 2y = -1. $$
Now we add $$2y$$ to both sides, yielding
$$ x(y-1) = 2y - 1. $$
Because every $$y \in B$$ satisfies $$y \neq 1$$, the coefficient $$(y-1)$$ is never zero, so we can safely divide by it. Doing so gives us the explicit solution
$$ x = \dfrac{2y-1}{y-1}. $$
The obtained expression is defined for every $$y \neq 1$$, and that is precisely the set $$B$$. We also observe that the value $$x=\dfrac{2y-1}{y-1}$$ can never equal $$2$$, for if it did we would have
$$ 2 = \dfrac{2y-1}{y-1}. $$
Cross-multiplying that hypothetical equality yields $$2y-2=2y-1,$$ which simplifies to $$-2=-1,$$ an impossibility. Hence $$x \neq 2$$, so $$x \in A$$. Therefore, for every $$y\in B$$ we have located an $$x\in A$$ satisfying $$f(x)=y$$, and surjectivity is proved.
Having shown both injectivity and surjectivity, we conclude that $$f$$ is bijective, i.e., invertible. The algebraic manipulation above already produced the inverse correspondence. We merely rewrite it in the standard inverse notation. By definition of an inverse, if $$y=f(x)$$, then $$x=f^{-1}(y)$$. The equation we derived was
$$ x = \dfrac{2y-1}{y-1}. $$
So the inverse function is
$$ f^{-1}(y)=\dfrac{2y-1}{y-1}, \qquad y \in B = \mathbb R-\{1\}. $$
This formula matches exactly what is written in Option D. No other option provides the correct inverse expression, and we have rigorously demonstrated both the bijectivity and the precise inverse.
Hence, the correct answer is Option D.
The contrapositive of the statement 'If two numbers are not equal, then their squares are not equal', is
Let the two numbers be represented by the real variables $$a$$ and $$b$$.
Define the following two simple statements:
$$P : a \ne b \quad\text{(the numbers are not equal)}$$
$$Q : a^{2} \ne b^{2} \quad\text{(the squares are not equal)}$$
The sentence given in the question, “If two numbers are not equal, then their squares are not equal”, is therefore written symbolically as
$$P \rightarrow Q.$$
To form the contrapositive, recall the logical rule that the contrapositive of any implication $$P \rightarrow Q$$ is $$\lnot Q \rightarrow \lnot P.$$ Here $$\lnot$$ means “not”. We now compute each negation explicitly.
Starting with $$Q$$:
$$Q : a^{2} \ne b^{2}$$
$$\therefore \;\lnot Q : a^{2} = b^{2}$$
Next, deal with $$P$$:
$$P : a \ne b$$
$$\therefore \;\lnot P : a = b$$
Substituting these negations into $$\lnot Q \rightarrow \lnot P$$ gives
$$a^{2} = b^{2} \rightarrow a = b.$$
Expressed verbally, this reads:
“If the squares of two numbers are equal, then the numbers are equal.”
Comparing with the options provided, this statement matches Option D.
Hence, the correct answer is Option D.
The statement $$p \to q \to (\sim p \to q \to q)$$ is
We have the propositional statement
$$p \;\rightarrow\; q \;\rightarrow\; (\,\sim p \;\rightarrow\; q \;\rightarrow\; q\,).$$
The implication sign $$\rightarrow$$ is taken to be right-associative, so an expression like $$a \rightarrow b \rightarrow c$$ is interpreted as $$a \rightarrow (\,b \rightarrow c\,).$$ Using this convention, our statement can be rewritten (placing all invisible parentheses explicitly) as
$$p \;\rightarrow\; \bigl(\,q \;\rightarrow\; \bigl(\,(\sim p) \;\rightarrow\; (\,q \;\rightarrow\; q\,)\bigr)\bigr).$$
Now we proceed from the innermost part and gradually simplify.
First, consider the sub-statement $$q \;\rightarrow\; q.$$
• By the truth table for implication, a statement of the form $$A \rightarrow A$$ is always true, because:
• If $$A$$ is true, then $$A \rightarrow A$$ has true antecedent and true consequent, so it is true.
• If $$A$$ is false, then $$A \rightarrow A$$ has false antecedent, and an implication with a false antecedent is true.
Hence
$$q \;\rightarrow\; q \equiv \text{T},$$
where “T” denotes the truth constant “always true”.
Substituting this result into the expression, we obtain
$$p \;\rightarrow\; \bigl(\,q \;\rightarrow\; \bigl(\,(\sim p) \;\rightarrow\; \text{T}\bigr)\bigr).$$
Next, look at the part $$(\sim p) \;\rightarrow\; \text{T}.$$
• A basic property of implication is: a statement of the form $$A \rightarrow \text{T}$$ is always true, because its consequent is true regardless of $$A$$. Therefore
$$(\sim p) \;\rightarrow\; \text{T} \equiv \text{T}.$$
Replacing this with “T”, the larger expression simplifies to
$$p \;\rightarrow\; \bigl(\,q \;\rightarrow\; \text{T}\bigr).$$
Again apply the same rule to $$q \;\rightarrow\; \text{T}$$: since the consequent is “T”, we have
$$q \;\rightarrow\; \text{T} \equiv \text{T}.$$
This leaves the outermost implication:
$$p \;\rightarrow\; \text{T}.$$
And finally, by the very same principle, any implication whose consequent is “T” is itself always true, so
$$p \;\rightarrow\; \text{T} \equiv \text{T}.$$
Thus every possible truth-value assignment to $$p$$ and $$q$$ makes the given statement true. Therefore the original statement is a tautology.
Hence, the correct answer is Option A.
The proposition $$(\sim p) \vee (p \wedge \sim q)$$ is equivalent to:
We begin with the given compound proposition
$$ (\sim p)\,\vee\,(p \wedge \sim q). $$
Our goal is to simplify it step by step, using the standard Boolean algebra (logical algebra) identities. The symbols have their usual meanings: $$\sim$$ denotes negation, $$\vee$$ denotes disjunction (OR), and $$\wedge$$ denotes conjunction (AND).
First, we recall the distributive law of logic, stated as
$$ A \;\vee\; (B \wedge C) \;\equiv\; (A \vee B)\; \wedge\; (A \vee C). $$
Here we can identify $$A = \sim p,$$ $$B = p,$$ and $$C = \sim q.$$ Substituting these into the distributive law, we obtain
$$ (\sim p) \;\vee\; (p \wedge \sim q) \;\equiv\; (\sim p \,\vee\, p)\; \wedge\; (\sim p \,\vee\, \sim q). $$
Next, notice that the expression $$\sim p \,\vee\, p$$ is a tautology because a statement OR its negation is always true. Symbolically,
$$ \sim p \,\vee\, p \;\equiv\; \text{True}. $$
When we have a conjunction in which one of the factors is the tautology, the whole conjunction reduces to the other factor. That is, $$\text{True} \wedge X \equiv X.$$ Therefore,
$$ (\sim p \,\vee\, p)\; \wedge\; (\sim p \,\vee\, \sim q) \;\equiv\; \text{True} \wedge (\sim p \,\vee\, \sim q) \;\equiv\; (\sim p \,\vee\, \sim q). $$
So we have shown
$$ (\sim p) \,\vee\, (p \wedge \sim q) \;\equiv\; (\sim p \,\vee\, \sim q). $$
Now we recognize another standard logical equivalence: the implication form. The implication
$$ p \to \sim q $$
is, by definition, equivalent to the disjunction
$$ \sim p \,\vee\, \sim q. $$
Since we have just derived the very same disjunction, it follows directly that
$$ (\sim p) \,\vee\, (p \wedge \sim q) \;\equiv\; p \to \sim q. $$
Thus, the original proposition is logically equivalent to the implication $$p \to \sim q,$$ which corresponds to Option A.
Hence, the correct answer is Option A.
The function $$f : N \to I$$ defined by $$f(x) = x - 5\left[\frac{x}{5}\right]$$, where $$N$$ is the set of natural numbers and $$[x]$$ denotes the greatest integer less than or equal to $$x$$, is:
Let $$x$$ be any natural number. Divide $$x$$ by $$5$$ using the usual division algorithm.
There exist unique integers $$q$$ and $$r$$ such that
$$x = 5q + r,$$
where $$q = \left[\dfrac{x}{5}\right]$$ and the remainder $$r$$ satisfies $$0 \le r \lt 5.$$ Explicitly, $$r \in \{0,1,2,3,4\}.$$
Substituting $$x = 5q + r$$ into the definition of the function gives
$$\begin{aligned} f(x) &= x - 5\left[\dfrac{x}{5}\right] \\ &= (5q + r) - 5q \\ &= r. \end{aligned}$$
Thus every natural number is sent to its remainder upon division by $$5,$$ and so
$$\text{Range}(f)=\{0,1,2,3,4\}.$$
To test injectivity (one-one), take two natural numbers that leave the same remainder when divided by $$5.$$ For instance, choose $$x_1 = 2$$ and $$x_2 = 7.$$ Both satisfy
$$f(2)=2,\qquad f(7)=2.$$
Since $$x_1 \ne x_2$$ but $$f(x_1)=f(x_2),$$ the function fails the injectivity criterion. Hence $$f$$ is not one-one.
To test surjectivity (onto) with respect to the stated codomain $$I$$ (the set of all integers), observe that
$$\text{Range}(f)=\{0,1,2,3,4\}\subsetneq I.$$
An integer such as $$6$$ lies in $$I$$ but never appears as an output, because every value of $$f$$ is at most $$4.$$ Therefore the function is not onto.
Because $$f$$ is neither one-one nor onto, the correct choice is the one that says “neither one-one nor onto.”
Hence, the correct answer is Option C.
The function $$f : R \to \left(-\frac{1}{2}, \frac{1}{2}\right)$$ defined as $$f(x) = \frac{x}{1+x^{2}}$$, is:
We are given the real-valued function
$$f:\; \mathbb R \;\rightarrow\; \left(-\dfrac12,\dfrac12\right), \qquad f(x)=\dfrac{x}{1+x^{2}}.$$
First we analyse the possible output values (the range) of the function, because this will tell us whether every element of the stated codomain $$\left(-\dfrac12,\dfrac12\right)$$ is actually attained.
To locate maximum and minimum values we differentiate. For a quotient $$\dfrac{u(x)}{v(x)}$$ the quotient rule says
$$\left(\dfrac{u}{v}\right)'=\dfrac{u'v-u\,v'}{v^{2}}.$$
Here $$u(x)=x$$ and $$v(x)=1+x^{2}$$, so $$u'(x)=1$$ and $$v'(x)=2x$$. Substituting into the rule gives
$$f'(x)=\dfrac{1\cdot(1+x^{2})-x\cdot 2x}{(1+x^{2})^{2}} =\dfrac{1+x^{2}-2x^{2}}{(1+x^{2})^{2}} =\dfrac{1-x^{2}}{(1+x^{2})^{2}}.$$
The numerator $$1-x^{2}=0$$ when $$x=\pm1$$, so the critical points are $$x=-1$$ and $$x=1$$. We evaluate $$f$$ there:
$$f(1)=\dfrac{1}{1+1^{2}}=\dfrac12, \qquad f(-1)=\dfrac{-1}{1+(-1)^{2}}=-\dfrac12.$$
Because the denominator $$\,(1+x^{2})^{2}\gt 0$$ for every real $$x$$, the sign of $$f'(x)$$ is the sign of $$1-x^{2}$$. Thus
$$ \begin{cases} f'(x)\gt 0 &\text{for }|x|\lt 1,\\[4pt] f'(x)\lt 0 &\text{for }|x|\gt 1. \end{cases} $$
So the function increases on $$(-1,1)$$, decreases on $$(-\infty,-1)$$ and on $$(1,\infty)$$. The point $$x=1$$ therefore gives a global maximum $$\dfrac12$$, and $$x=-1$$ gives a global minimum $$-\dfrac12$$. As $$x\rightarrow\pm\infty$$ we have
$$\lim_{x\to\pm\infty}\dfrac{x}{1+x^{2}} =\lim_{x\to\pm\infty}\dfrac{1}{x+1/x} =0,$$
so the graph approaches the $$x$$-axis from both sides without touching it.
Combining all this information, the set of output values is the open interval
$$\left(-\dfrac12,\dfrac12\right).$$
Because the codomain stated in the question is exactly this interval, every element of the codomain appears as an output. Hence the function is surjective (onto).
Next we test whether the function is one-one (injective). A continuous function that first decreases, then increases, and then decreases again cannot be monotonic on the whole of $$\mathbb R$$, so it is very likely not injective. We confirm this by finding two different inputs that give the same output.
Let us choose the value $$y=\dfrac25=0.4$$, which lies strictly between $$0$$ and $$\dfrac12$$. We solve the equation $$f(x)=y$$ algebraically.
Starting from $$\displaystyle y=\dfrac{x}{1+x^{2}}$$ we cross-multiply:
$$y(1+x^{2})=x \;\;\Longrightarrow\;\; y + yx^{2} - x = 0.$$
This is a quadratic in $$x$$:
$$y\,x^{2} - x + y = 0.$$
For a quadratic $$ax^{2}+bx+c=0$$ the solutions are given by the quadratic formula
$$x=\dfrac{-b\pm\sqrt{b^{2}-4ac}}{2a}.$$
In our case $$a=y,\,b=-1,\,c=y$$, so
$$x=\dfrac{-(-1)\pm\sqrt{(-1)^{2}-4y^{2}}}{2y} =\dfrac{1\pm\sqrt{1-4y^{2}}}{2y}.$$
Because $$0\lt y\lt \dfrac12$$, the discriminant $$1-4y^{2}$$ is positive, giving two distinct real solutions. Putting our specific choice $$y=\dfrac25$$, we get
$$x_{1}=\dfrac{1-\sqrt{1-\dfrac{16}{25}}}{\dfrac{4}{5}} =\dfrac{1-\sqrt{\dfrac{9}{25}}}{\dfrac45} =\dfrac{1-\dfrac35}{\dfrac45} =\dfrac{\dfrac25}{\dfrac45} =\dfrac12,$$
and
$$x_{2}=\dfrac{1+\sqrt{1-\dfrac{16}{25}}}{\dfrac45} =\dfrac{1+\dfrac35}{\dfrac45} =\dfrac{\dfrac85}{\dfrac45} =2.$$
Thus $$f\!\left(\dfrac12\right)=\dfrac25=f(2).$$ Two different inputs map to the same output, so the function is not injective.
We have shown that
• $$f$$ is surjective onto its codomain $$\left(-\dfrac12,\dfrac12\right)$$,
• $$f$$ is not injective.
Therefore $$f$$ is surjective but not injective, which corresponds to Option C.
Hence, the correct answer is Option C.
Let $$a, b, c \in R$$. If $$f(x) = ax^{2} + bx + c$$ is such that $$a + b + c = 3$$ and $$f(x + y) = f(x) + f(y) + xy$$, $$\forall$$ $$x, y \in R$$, then $$\sum_{n=1}^{10} f(n)$$ is equal to:
We are told that $$f(x)=ax^{2}+bx+c$$ with real constants $$a,b,c$$ satisfies two conditions:
1. $$a+b+c=3$$.
2. $$f(x+y)=f(x)+f(y)+xy$$ for every real pair $$x,y$$.
First we expand the left-hand side of the functional equation. Taking $$f(x)=ax^{2}+bx+c$$ we get
$$ \begin{aligned} f(x+y)&=a(x+y)^{2}+b(x+y)+c \\ &=a(x^{2}+2xy+y^{2})+bx+by+c \\ &=ax^{2}+2axy+ay^{2}+bx+by+c. \end{aligned} $$
Next we write the right-hand side, namely $$f(x)+f(y)+xy$$. Computing separately,
$$ \begin{aligned} f(x)+f(y) &=\bigl(ax^{2}+bx+c\bigr)+\bigl(ay^{2}+by+c\bigr) \\ &=ax^{2}+ay^{2}+bx+by+2c. \end{aligned} $$
Adding the extra $$xy$$ term required by the equation, we obtain
$$f(x)+f(y)+xy=ax^{2}+ay^{2}+bx+by+2c+xy.$$
Because the functional equation holds for all real $$x,y$$, the two expanded expressions must match term by term. We therefore equate coefficients of each power of $$x$$ and $$y$$:
• Coefficient of $$x^{2}$$: $$a=a$$ (already consistent).
• Coefficient of $$y^{2}$$: $$a=a$$ (already consistent).
• Coefficient of the mixed term $$xy$$: we have $$2a$$ on the left and $$1$$ on the right, so
$$2a=1 \;\;\Longrightarrow\;\; a=\dfrac12.$$
• Constant term: left side has $$c$$ whereas right side has $$2c$$, hence
$$c=2c \;\;\Longrightarrow\;\; c=0.$$
With $$a=\dfrac12$$ and $$c=0$$ found, we use the earlier restriction $$a+b+c=3$$ to determine $$b$$:
$$ \frac12 + b + 0 = 3 \;\;\Longrightarrow\;\; b = 3-\frac12 = \frac52. $$
Thus the concrete quadratic is
$$f(x)=\frac12x^{2}+\frac52x.$$
Now we need the sum $$\displaystyle\sum_{n=1}^{10}f(n)$$. Substituting our explicit form,
$$ \sum_{n=1}^{10}f(n) =\sum_{n=1}^{10}\left(\frac12n^{2}+\frac52n\right) =\frac12\sum_{n=1}^{10}n^{2}+\frac52\sum_{n=1}^{10}n. $$
We recall the standard summation formulas (stated here for clarity):
• $$\displaystyle\sum_{n=1}^{N} n = \frac{N(N+1)}{2}.$$
• $$\displaystyle\sum_{n=1}^{N} n^{2} = \frac{N(N+1)(2N+1)}{6}.$$
Taking $$N=10$$, we compute each:
$$ \sum_{n=1}^{10} n = \frac{10\cdot11}{2}=55, \qquad \sum_{n=1}^{10} n^{2} = \frac{10\cdot11\cdot21}{6}=385. $$
Substituting these values back, we get
$$ \begin{aligned} \sum_{n=1}^{10}f(n) &=\frac12\,(385)+\frac52\,(55) \\ &=\frac{385}{2}+\frac{275}{2} \\ &=\frac{660}{2}=330. \end{aligned} $$
Hence, the correct answer is Option A.
Let $$f(x) = 2^{10}x + 1$$ and $$g(x) = 3^{10}x - 1$$. If $$(fog)(x) = x$$, then $$x$$ is equal to:
We are given two linear functions.
First function: $$f(x)=2^{10}x+1.$$ Second function: $$g(x)=3^{10}x-1.$$
The statement $$(fog)(x)=x$$ means composition; that is, we must substitute $$g(x)$$ into $$f(x)$$ and equate the result to $$x$$. By definition of composition,
$$ (fog)(x)=f\!\left(g(x)\right). $$
Now we actually perform this substitution. Wherever we see an $$x$$ in $$f(x)=2^{10}x+1$$ we replace it by $$g(x)=3^{10}x-1$$:
$$ f\!\left(g(x)\right)=2^{10}\bigl(g(x)\bigr)+1 =2^{10}\bigl(3^{10}x-1\bigr)+1. $$
The condition tells us that this must equal $$x$$, hence
$$ 2^{10}\bigl(3^{10}x-1\bigr)+1 = x. $$
We expand the left-hand side:
$$ 2^{10}\cdot3^{10}x - 2^{10} + 1 = x. $$
Collect all terms on one side so that everything involving $$x$$ is together:
$$ 2^{10}3^{10}x - x - 2^{10} + 1 = 0. $$
Factor out $$x$$ from the first two terms:
$$ x\bigl(2^{10}3^{10}-1\bigr) -\bigl(2^{10}-1\bigr)=0. $$
Now isolate $$x$$ by adding $$2^{10}-1$$ to both sides and then dividing:
$$ x\bigl(2^{10}3^{10}-1\bigr)=2^{10}-1, $$
so
$$ x=\frac{2^{10}-1}{2^{10}3^{10}-1}. $$
The fraction still does not look exactly like any option because the options contain negative exponents. We therefore manipulate our expression to reveal that form.
Notice that multiplying the numerator and denominator by $$2^{-10}$$ will introduce the reciprocals required. Explicitly:
$$ x=\frac{2^{10}-1}{2^{10}3^{10}-1}\times\frac{2^{-10}}{2^{-10}} =\frac{(2^{10}-1)2^{-10}}{(2^{10}3^{10}-1)2^{-10}}. $$
Compute each product:
Numerator:
$$ (2^{10}-1)2^{-10}=2^{10}2^{-10}-1\cdot2^{-10}=1-2^{-10}. $$
Denominator:
$$ (2^{10}3^{10}-1)2^{-10}=3^{10}(2^{10}2^{-10})-1\cdot2^{-10}=3^{10}-2^{-10}. $$
Therefore
$$ x=\frac{1-2^{-10}}{3^{10}-2^{-10}}. $$
This is exactly the expression listed in Option B.
Hence, the correct answer is Option B.
The Boolean Expression $$(p \wedge \sim q) \vee q \vee (\sim p \wedge q)$$ is equivalent to
We have to simplify the Boolean expression $$E=(p \wedge \sim q)\; \vee\; q\; \vee\; (\sim p \wedge q)$$ and compare the result with the four alternatives.
Because the $$\vee$$ (OR) and $$\wedge$$ (AND) operations are both commutative and associative, we may rearrange the terms without changing the value. Thus we write
$$E \;=\; q \;\vee\; (p \wedge \sim q) \;\vee\; (\sim p \wedge q).$$
Now notice the presence of the term $$q$$ by itself and the compound term $$(\sim p \wedge q).$$ The absorption law of Boolean algebra states that
$$x \;\vee\; (y \wedge x) \;=\; x.$$
Here, let us set $$x = q$$ and $$y = \sim p.$$ Applying the absorption law, we obtain
$$q \;\vee\; (\sim p \wedge q) = q.$$
Substituting this result back into the full expression gives
$$E \;=\; q \;\vee\; (p \wedge \sim q).$$
At this stage, only two terms remain. To proceed further we invoke the distributive law, which in Boolean form states
$$a \;\vee\; (b \wedge c) \;=\; (a \vee b) \;\wedge\; (a \vee c).$$
Assigning $$a = q,\; b = p,\; c = \sim q,$$ we have
$$q \;\vee\; (p \wedge \sim q)\;=\;(q \vee p)\;\wedge\;(q \vee \sim q).$$
The expression $$(q \vee \sim q)$$ is always true (a tautology), because either $$q$$ is true or $$\sim q$$ is true. In Boolean algebra, a tautology is represented by $$1$$. Therefore,
$$(q \vee p)\;\wedge\;1 \;=\; q \vee p.$$
Since the OR operation is commutative, $$q \vee p = p \vee q.$$ Hence the completely simplified form of the original expression is
$$E = p \vee q.$$
Looking at the options provided, this matches Option A.
Hence, the correct answer is Option A.
The contrapositive of the following statement, "If the side of a square doubles, then its area increases four times", is
We begin by identifying the two simple statements that form the given conditional sentence.
Let $$P$$ be the statement “the side of a square doubles”.
Let $$Q$$ be the statement “its area increases four times”.
The original sentence can be written symbolically as the implication $$P \rightarrow Q$$, which reads “If $$P$$ is true, then $$Q$$ is true”.
Now we recall the logical rule for forming a contrapositive. For any implication $$P \rightarrow Q$$, the contrapositive is obtained by first negating both parts and then reversing their order. In symbols, the contrapositive is $$\lnot Q \rightarrow \lnot P$$.
So, applying this rule to our two statements, we have
$$\lnot Q \rightarrow \lnot P$$
where
$$\lnot Q:$$ “the area of a square does not increase four times”,
$$\lnot P:$$ “its side is not doubled”.
Substituting these English negations back into the logical form, we obtain the plain-language contrapositive:
“If the area of a square does not increase four times, then its side is not doubled.”
Comparing this sentence with the four options given:
Option A says: “if the area of a square increases four times, then its side is not doubled.” This keeps $$Q$$ but negates $$P$$, so it is the converse of the inverse, not the contrapositive.
Option B says: “if the area of a square increases four times, then its side is doubled.” That is exactly the original implication $$P \rightarrow Q$$ written in reverse English order; it is the converse, not the contrapositive.
Option C says: “if the area of a square does not increase four times, then its side is not doubled.” This matches $$\lnot Q \rightarrow \lnot P$$ perfectly, so it is the true contrapositive.
Option D says: “if the side of a square is not doubled, then its area does not increase four times.” This has the correct negations but does not reverse the order; it is the inverse, not the contrapositive.
Hence, the correct answer is Option C.
Consider the following two statements:
$$P$$: If 7 is an odd number, then 7 is divisible by 2.
$$Q$$: If 7 is a prime number, then 7 is an odd number.
If $$V_1$$ is the truth value of the contrapositive of $$P$$ and $$V_2$$ is the truth value of contrapositive of $$Q$$, then the ordered pair $$(V_1, V_2)$$ equals
First, we recall the standard logical rule: for any implication of the form $$A \rightarrow B$$ the contrapositive is the statement $$\lnot B \rightarrow \lnot A$$ and both have exactly the same truth value. We will apply this rule separately to the two given statements $$P$$ and $$Q$$, and then determine the ordered pair of their truth values.
We have the statement $$P$$:
$$P:\qquad$$ If $$7$$ is an odd number, then $$7$$ is divisible by $$2.$$
For $$P$$ the antecedent (the “if” part) is
$$A:\;7\text{ is an odd number},$$
and the consequent (the “then” part) is
$$B:\;7\text{ is divisible by }2.$$
Using the contrapositive rule, the contrapositive of $$P$$ is
$$\lnot B \rightarrow \lnot A.$$
Writing it out in words:
If $$7$$ is \emph{not $$divisible by }2,$$ then $$7$$ is \emph{not $$an odd number}.$$
Now, we determine the truth value of this contrapositive:
• The statement “7 is not divisible by 2” is true because 7 divided by 2 does not give an integer quotient.
• The statement “7 is not an odd number” is false because 7 is indeed odd.
In a conditional $$X \rightarrow Y,$$ if the antecedent $$X$$ is true and the consequent $$Y$$ is false, the whole conditional is false. Therefore, the contrapositive of $$P$$ is false. We denote this by
$$V_1 = F.$$
Next, we analyze the statement $$Q$$:
$$Q:\qquad$$ If $$7$$ is a prime number, then $$7$$ is an odd number $$.$$
Here, the antecedent is
$$C:\;7\text{ is a prime number},$$
and the consequent is
$$D:\;7\text{ is an odd number}.$$
The contrapositive of $$Q$$ is
$$\lnot D \rightarrow \lnot C,$$
that is,
If $$7$$ is \emph{not $$an odd number, then }7$$ is \emph{not $$a prime number}.$$
We check its truth value:
• The antecedent “7 is not an odd number” is false because 7 is odd.
• In material implication, whenever the antecedent is false, the entire conditional statement is automatically true, regardless of the consequent.
Hence the contrapositive of $$Q$$ is true, and we write
$$V_2 = T.$$
Collecting the two truth values, we obtain the ordered pair
$$(V_1, V_2) = (F, T).$$
This matches Option A.
Hence, the correct answer is Option A.
For $$x \in R$$, $$x \neq 0$$, $$x \neq 1$$, let $$f_0(x) = \frac{1}{1-x}$$ and $$f_{n+1}(x) = f_0(f_n(x))$$, $$n = 0, 1, 2, \ldots$$. Then the value of $$f_{100}(3) + f_1\left(\frac{2}{3}\right) + f_2\left(\frac{3}{2}\right)$$ is equal to:
We are given the function $$ f_0(x) = \frac{1}{1-x} $$ for $$ x \in \mathbb{R} $$, $$ x \neq 0 $$, $$ x \neq 1 $$, and the recursive definition $$ f_{n+1}(x) = f_0(f_n(x)) $$ for $$ n = 0, 1, 2, \ldots $$. We need to find the value of $$ f_{100}(3) + f_1\left(\frac{2}{3}\right) + f_2\left(\frac{3}{2}\right) $$.
First, we compute the first few functions to identify a pattern. Start with $$ f_0(x) $$:
$$ f_0(x) = \frac{1}{1-x} $$
Now, compute $$ f_1(x) = f_0(f_0(x)) $$:
$$ f_1(x) = f_0\left( \frac{1}{1-x} \right) = \frac{1}{1 - \frac{1}{1-x}} $$
Simplify the denominator:
$$ 1 - \frac{1}{1-x} = \frac{1-x}{1-x} - \frac{1}{1-x} = \frac{(1-x) - 1}{1-x} = \frac{-x}{1-x} $$
So,
$$ f_1(x) = \frac{1}{\frac{-x}{1-x}} = \frac{1-x}{-x} = -\frac{1-x}{x} = \frac{x-1}{x} $$
Next, compute $$ f_2(x) = f_0(f_1(x)) $$:
$$ f_2(x) = f_0\left( \frac{x-1}{x} \right) = \frac{1}{1 - \frac{x-1}{x}} $$
Simplify the denominator:
$$ 1 - \frac{x-1}{x} = \frac{x}{x} - \frac{x-1}{x} = \frac{x - (x-1)}{x} = \frac{1}{x} $$
So,
$$ f_2(x) = \frac{1}{\frac{1}{x}} = x $$
Now, compute $$ f_3(x) = f_0(f_2(x)) $$:
$$ f_3(x) = f_0(f_2(x)) = f_0(x) = \frac{1}{1-x} $$
This is the same as $$ f_0(x) $$. Similarly,
$$ f_4(x) = f_0(f_3(x)) = f_0\left( \frac{1}{1-x} \right) = f_1(x) = \frac{x-1}{x} $$
$$ f_5(x) = f_0(f_4(x)) = f_0\left( \frac{x-1}{x} \right) = f_2(x) = x $$
We observe that the functions repeat every 3 steps: $$ f_3 = f_0 $$, $$ f_4 = f_1 $$, $$ f_5 = f_2 $$, and so on. Thus, the sequence is periodic with period 3, meaning:
$$ f_n(x) = f_{n \mod 3}(x) $$
where:
- If $$ n \equiv 0 \pmod{3} $$, then $$ f_n(x) = f_0(x) = \frac{1}{1-x} $$
- If $$ n \equiv 1 \pmod{3} $$, then $$ f_n(x) = f_1(x) = \frac{x-1}{x} $$
- If $$ n \equiv 2 \pmod{3} $$, then $$ f_n(x) = f_2(x) = x $$
Now, we compute each term in the expression $$ f_{100}(3) + f_1\left(\frac{2}{3}\right) + f_2\left(\frac{3}{2}\right) $$.
First, for $$ f_{100}(3) $$:
Find $$ 100 \mod 3 $$: $$ 100 \div 3 = 33 \times 3 = 99 $$, remainder $$ 100 - 99 = 1 $$, so $$ 100 \equiv 1 \pmod{3} $$. Thus, $$ f_{100}(3) = f_1(3) $$.
Using $$ f_1(x) = \frac{x-1}{x} $$:
$$ f_1(3) = \frac{3-1}{3} = \frac{2}{3} $$
So, $$ f_{100}(3) = \frac{2}{3} $$.
Second, for $$ f_1\left(\frac{2}{3}\right) $$:
Using $$ f_1(x) = \frac{x-1}{x} $$:
$$ f_1\left(\frac{2}{3}\right) = \frac{\frac{2}{3} - 1}{\frac{2}{3}} = \frac{-\frac{1}{3}}{\frac{2}{3}} = -\frac{1}{3} \times \frac{3}{2} = -\frac{1}{2} $$
Third, for $$ f_2\left(\frac{3}{2}\right) $$:
Since $$ f_2(x) = x $$:
$$ f_2\left(\frac{3}{2}\right) = \frac{3}{2} $$
Now, sum the terms:
$$ f_{100}(3) + f_1\left(\frac{2}{3}\right) + f_2\left(\frac{3}{2}\right) = \frac{2}{3} + \left(-\frac{1}{2}\right) + \frac{3}{2} $$
Combine the terms step by step. First, combine the fractions with denominator 2:
$$ -\frac{1}{2} + \frac{3}{2} = \frac{-1 + 3}{2} = \frac{2}{2} = 1 $$
Then add to $$ \frac{2}{3} $$:
$$ \frac{2}{3} + 1 = \frac{2}{3} + \frac{3}{3} = \frac{5}{3} $$
Hence, the value is $$ \frac{5}{3} $$. Comparing with the options:
A. $$ \frac{8}{3} $$
B. $$ \frac{4}{3} $$
C. $$ \frac{5}{3} $$
D. $$ \frac{1}{3} $$
So, the correct answer is Option C.
If $$f(x) + 2f\left(\frac{1}{x}\right) = 3x$$, $$x \neq 0$$, and $$S = \{x \in R : f(x) = f(-x)\}$$, then $$S$$
We are given the functional equation
$$f(x)+2f\!\left(\frac1x\right)=3x,\qquad x\neq0.$$
Our aim is to determine the set
$$S=\{x\in\mathbb R\;:\;f(x)=f(-x)\}.$$
First we must obtain an explicit expression for $$f(x).$$ To do this we write the given relation once for $$x$$ and once for $$\dfrac1x$$.
For $$x$$ itself we already have
$$f(x)+2f\!\left(\frac1x\right)=3x\qquad\text{(1)}.$$
Now replace $$x$$ by $$\dfrac1x$$ everywhere in (1). Because $$x\neq0$$, this substitution is legitimate and yields
$$f\!\left(\frac1x\right)+2f(x)=\frac3x\qquad\text{(2)}.$$
Thus we have a pair of simultaneous linear equations in the two unknowns
$$A=f(x),\qquad B=f\!\left(\frac1x\right).$$
Written explicitly, the system is
$$\begin{cases} A+2B=3x,\\[4pt] 2A+B=\dfrac3x. \end{cases}$$
We now solve this system. From elementary algebra, when we have
$$\begin{cases} A+2B=C_1,\\ 2A+B=C_2, \end{cases}$$
the solution is obtained by elimination. Multiplying the first equation by $$2$$ gives
$$2A+4B=6x\qquad\text{(3)}.$$
Subtract (2) from (3):
$$\bigl(2A+4B\bigr)-\bigl(2A+B\bigr)=6x-\frac3x.$$
The left‐hand side simplifies to $$3B$$, so
$$3B=6x-\frac3x.$$
Dividing by $$3$$ gives
$$B=2x-\frac1x.$$
Thus
$$f\!\left(\frac1x\right)=2x-\frac1x.$$
We substitute this value of $$B$$ back into equation (1):
$$A+2\left(2x-\frac1x\right)=3x.$$
Expanding the brackets we get
$$A+4x-\frac2x=3x.$$
Now isolate $$A$$ (which is $$f(x)$$):
$$A=3x-4x+\frac2x=-x+\frac2x.$$
So we have obtained an explicit formula valid for every non-zero real number:
$$f(x)=-x+\frac2x,\qquad x\neq0.$$
With the function in hand, we can now find $$S.$$ By definition,
$$f(x)=f(-x).$$
Using our formula for $$f$$ on both sides, we write
$$-x+\frac2x \;=\; -(-x)+\frac2{-x}.$$
Carefully simplifying the right‐hand side:
$$-(-x)=x,\qquad\frac2{-x}=-\frac2x,$$
so the equality becomes
$$-x+\frac2x = x-\frac2x.$$
To clear the denominators we multiply both sides by $$x$$ (remember, $$x\neq0$$):
$$x\!\left(-x+\frac2x\right)=x\!\left(x-\frac2x\right).$$
Performing the multiplication term by term, we obtain
$$-x^2+2 = x^2-2.$$
Now we move all terms to one side:
$$-x^2+2-(x^2-2)=0\quad\Longrightarrow\quad -x^2+2-x^2+2=0.$$
This simplifies to
$$-2x^2+4=0.$$
Dividing by $$-2$$ gives
$$x^2-2=0.$$
Finally, solving for $$x$$ we get
$$x^2=2\quad\Longrightarrow\quad x=\pm\sqrt2.$$
Both solutions are non-zero real numbers, so they are admissible. No other real numbers satisfy the equality $$f(x)=f(-x).$$
Therefore
$$S=\{\sqrt2,\,-\sqrt2\},$$
which clearly contains exactly two elements.
Hence, the correct answer is Option A.
Asn (N-terminus): Contains a free primary amine ($$-NH_2$$) and a side-chain primary amide ($$-CONH_2$$).
Ser (C-terminus): Contains a side-chain hydroxyl group ($$-OH$$).
Acetic anhydride ($$Ac_2O$$) in excess acts as a powerful acetylating agent. In the presence of a base ($$Et_3N$$), it replaces the active hydrogen atoms of nucleophilic functional groups with acetyl groups ($$-COCH_3$$ or $$-Ac$$).
Under excess conditions, all accessible nucleophilic sites are acetylated:
N-terminal Amine: $$-NH_2 \xrightarrow{Ac_2O} -NHCOCH_3$$ (Forms an acetamide).
Serine Side-chain: $$-OH \xrightarrow{Ac_2O} -OCOCH_3$$ (Forms an ester).
Asparagine Side-chain: $$-CONH_2 \xrightarrow{Ac_2O} -CONH-COCH_3$$ (Primary amides are acetylated to $$N$$-acetyl amides when the reagent is in excess).
Option B is the correct product because it correctly shows the acetylation of all three reactive sites: the N-terminus, the serine hydroxyl, and the asparagine side-chain amide. The C-terminal carboxylic acid ($$-COOH$$) remains in its acidic form.
Let $$A = \{x_1, x_2, \ldots, x_7\}$$ and $$B = \{y_1, y_2, y_3\}$$ be two sets containing seven and three distinct elements respectively. Then the total number of functions $$f : A \rightarrow B$$ that are onto, if there exist exactly three elements $$x$$ in $$A$$ such that $$f(x) = y_2$$, is equal to:
We are asked to count all onto (surjective) functions $$f : A \rightarrow B$$ under the extra condition that exactly three elements of $$A$$ go to the element $$y_2 \in B$$. We begin by recalling what an onto function means. A function $$f$$ is onto when every element of the codomain $$B$$ has at least one pre-image in the domain $$A$$, i.e. for each $$y \in B$$ there exists at least one $$x \in A$$ with $$f(x) = y$$.
First we handle the condition about $$y_2$$. We are told that there are exactly three elements $$x$$ in $$A$$ such that $$f(x) = y_2$$. To choose which elements of $$A$$ they are, we compute
$$ ^7C_3 $$
because $$A$$ contains seven distinct elements and we must select three of them. After this choice is made, these three elements are permanently assigned the image $$y_2$$.
We now investigate what happens to the remaining elements of $$A$$. Once three elements are fixed for $$y_2$$, there are $$7 - 3 = 4$$ elements of $$A$$ left. Call this leftover set $$A'$$. These four elements must be mapped into the remaining two elements of $$B$$, namely $$y_1$$ and $$y_3$$.
Because the overall function is required to be onto, each of $$y_1$$ and $$y_3$$ must appear at least once as a value of $$f$$. So, when distributing the four elements of $$A'$$, neither $$y_1$$ nor $$y_3$$ can be missed. We count these distributions carefully.
For each of the four elements in $$A'$$ we have two immediate choices: send it to $$y_1$$ or send it to $$y_3$$. Ignoring the “at least once” restriction for the moment, this yields $$2^4$$ possibilities. Now we subtract the two unacceptable allocations—either “all go to $$y_1$$” or “all go to $$y_3$$”. Hence the number of admissible ways is
$$ 2^4 - 2 \;=\; 16 - 2 \;=\; 14. $$
Putting the two independent selections together—first the choice of which three elements map to $$y_2$$, and then the admissible distribution of the remaining four elements between $$y_1$$ and $$y_3$$—we multiply the counts:
$$ \text{Total onto functions} \;=\; {^7C_3} \times 14. $$
Thus the required number is $$14 \cdot {^7C_3}$$.
Hence, the correct answer is Option C.
The negation of $$\sim s \vee (\sim r \wedge s)$$ is equivalent to
We want the negation of the statement $$\sim s \vee (\sim r \wedge s)$$. In symbols we therefore start with
$$\neg\bigl(\,\sim s \;\vee\; (\sim r \wedge s)\bigr).$$
First recall De Morgan’s law for two statements: $$\neg(A\vee B)=\neg A\;\wedge\;\neg B.$$ Here we may identify
$$A=\sim s,\qquad B=(\sim r\wedge s).$$
Applying the law gives
$$\neg(\sim s\vee(\sim r\wedge s))=\neg(\sim s)\;\wedge\;\neg(\sim r\wedge s).$$
The first part simplifies directly because double negation cancels:
$$\neg(\sim s)=s.$$
So we now have
$$s\;\wedge\;\neg(\sim r\wedge s).$$
We still need to simplify the second negation. Again, by De Morgan’s law, but this time for a conjunction, $$\neg(A\wedge B)=\neg A\;\vee\;\neg B.$$ Taking
$$A=\sim r,\qquad B=s,$$
we get
$$\neg(\sim r\wedge s)=\neg(\sim r)\;\vee\;\neg s.$$
Double negation on the first term yields
$$\neg(\sim r)=r.$$
Thus
$$\neg(\sim r\wedge s)=r\;\vee\;\neg s.$$
Substituting this back, our whole expression is now
$$s\;\wedge\;(r\;\vee\;\neg s).$$
Next, we distribute the conjunction over the disjunction using the distributive law $$P\wedge(Q\vee R)=(P\wedge Q)\;\vee\;(P\wedge R).$$ Here $$P=s,\;Q=r,\;R=\neg s,$$ so we obtain
$$s\wedge(r\vee\neg s)=(s\wedge r)\;\vee\;(s\wedge\neg s).$$
However, $$s\wedge\neg s$$ is a contradiction and always evaluates to false, so that term can be dropped:
$$(s\wedge r)\;\vee\;\text{false}=s\wedge r.$$
We have therefore shown
$$\neg\bigl(\,\sim s \vee (\sim r \wedge s)\bigr)\equiv s\wedge r.$$
Hence, the correct answer is Option A.
Consider the following statements:
P: Suman is brilliant
Q: Suman is rich
R: Suman is honest
The negation of the statement, "Suman is brilliant and dishonest if and only if Suman is rich" can be equivalently expressed as
We are given three statements:
- P: Suman is brilliant
- Q: Suman is rich
- R: Suman is honest
The statement to negate is: "Suman is brilliant and dishonest if and only if Suman is rich".
First, note that "dishonest" means not honest, so it is represented as $$\sim R$$. Therefore, "Suman is brilliant and dishonest" is written as $$P \wedge \sim R$$.
The entire statement "Suman is brilliant and dishonest if and only if Suman is rich" is logically expressed as $$(P \wedge \sim R) \leftrightarrow Q$$.
We need to find the negation of this statement: $$\sim \left[ (P \wedge \sim R) \leftrightarrow Q \right]$$.
Recall that the negation of a biconditional $$A \leftrightarrow B$$ is equivalent to $$A \leftrightarrow \sim B$$. Applying this here, let $$A = P \wedge \sim R$$ and $$B = Q$$. Then:
$$\sim \left[ (P \wedge \sim R) \leftrightarrow Q \right] \equiv (P \wedge \sim R) \leftrightarrow \sim Q$$
Since the biconditional is commutative (i.e., $$X \leftrightarrow Y$$ is the same as $$Y \leftrightarrow X$$), we can rewrite this as:
$$\sim Q \leftrightarrow (P \wedge \sim R)$$
Now, comparing this with the given options:
- Option A: $$\sim Q \leftrightarrow \sim P \vee R$$
- Option B: $$\sim Q \leftrightarrow P \vee \sim R$$
- Option C: $$\sim Q \leftrightarrow P \wedge \sim R$$
- Option D: $$\sim Q \leftrightarrow \sim P \wedge R$$
Our expression $$\sim Q \leftrightarrow (P \wedge \sim R)$$ matches Option C exactly.
Therefore, the negation of the given statement is equivalently expressed as Option C.
Hence, the correct answer is Option C.
The contrapositive of the statement "If it is raining, then I will not come", is
We begin by recalling the fundamental logical rule about contrapositives. For any implication of the form $$P \Rightarrow Q$$, the contrapositive is obtained by simultaneously negating both the hypothesis and the conclusion and reversing their order. In symbols, the contrapositive of $$P \Rightarrow Q$$ is $$\neg Q \Rightarrow \neg P$$, where $$\neg$$ stands for “not.” This rule is routinely taught in elementary logic and is guaranteed to give a statement that is logically equivalent to the original implication.
In the given English sentence, the parts can be identified as follows:
• Hypothesis $$P$$ : “It is raining.”
• Conclusion $$Q$$ : “I will not come.”
Translating the original sentence into symbolic form, we have
$$P \Rightarrow Q$$
which reads “If it is raining, then I will not come.”
Now we apply the rule for the contrapositive. First we negate the conclusion $$Q$$. The conclusion “I will not come” is negated to become “I will come.” Symbolically, $$\neg Q$$ means “I will come.”
Next we negate the hypothesis $$P$$. The hypothesis “It is raining” is negated to become “It is not raining.” Symbolically, $$\neg P$$ means “It is not raining.”
Finally, we reverse the order, writing $$\neg Q$$ first and $$\neg P$$ second, and we retain the implication arrow $$\Rightarrow$$ between them. Thus the contrapositive is expressed symbolically as
$$\neg Q \Rightarrow \neg P$$
which translates back into English as
“If I will come, then it is not raining.”
Comparing this English sentence with the four options provided, we see that it matches exactly with Option A:
Option A. if I will come, then it is not raining.
Hence, the correct answer is Option A.
The contrapositive of the statement "if I am not feeling well, then I will go to the doctor" is:
To solve this problem, we need to find the contrapositive of the given statement: "if I am not feeling well, then I will go to the doctor."
First, recall that for any conditional statement of the form "If P, then Q," the contrapositive is "If not Q, then not P." The contrapositive is logically equivalent to the original statement.
Identify the components of the given statement:
- P: "I am not feeling well"
- Q: "I will go to the doctor"
So the statement is: If P, then Q.
Now, form the contrapositive: If not Q, then not P.
Determine not Q and not P:
- not Q: Negation of "I will go to the doctor" is "I will not go to the doctor."
- not P: Negation of "I am not feeling well" is "I am feeling well" (since two negatives cancel out).
Therefore, the contrapositive is: "If I will not go to the doctor, then I am feeling well."
Now, compare this with the options:
- Option A: "if I will go to the doctor, then I am not feeling well" → This is "If Q, then P," which is the converse, not the contrapositive.
- Option B: "if I am feeling well, then I will not go to the doctor" → This is "If not P, then not Q," which is the inverse, not the contrapositive.
- Option C: "if I will not go to the doctor, then I am feeling well" → This matches our contrapositive exactly: "If not Q, then not P."
- Option D: "if I will go to the doctor, then I am feeling well" → This is "If Q, then not P," which is neither the contrapositive nor logically equivalent.
Hence, the correct answer is Option C.
Let p, q, r denote arbitrary statements. Then the logically equivalent of the statement $$p \Rightarrow (q \vee r)$$ is:
We are given the statement $$ p \Rightarrow (q \vee r) $$ and need to find which option is logically equivalent to it. Remember that $$ a \Rightarrow b $$ is equivalent to $$ \sim a \vee b $$. So, let's rewrite the given statement:
$$ p \Rightarrow (q \vee r) = \sim p \vee (q \vee r) $$
Since disjunction (OR) is associative, we can write this as:
$$ \sim p \vee q \vee r $$
Now, we'll check each option by converting them into equivalent forms using the same implication rule.
Option A: $$ (p \vee q) \Rightarrow r $$
Rewrite the implication:
$$ (p \vee q) \Rightarrow r = \sim (p \vee q) \vee r $$
Apply De Morgan's law to $$ \sim (p \vee q) $$:
$$ (\sim p \wedge \sim q) \vee r $$
This is not the same as $$ \sim p \vee q \vee r $$ because it has a conjunction ($$\wedge$$) and different terms. For example, if $$ p $$ is false, $$ q $$ is false, and $$ r $$ is false, the original statement is true (since $$ \sim p $$ is true), but this expression becomes $$ (\text{true} \wedge \text{true}) \vee \text{false} = \text{true} \vee \text{false} = \text{true} $$. However, if $$ p $$ is true, $$ q $$ is false, and $$ r $$ is false, the original is false (true implies false), but this expression is $$ (\text{false} \wedge \text{true}) \vee \text{false} = \text{false} \vee \text{false} = \text{false} $$, which matches. But let's test another case: $$ p $$ false, $$ q $$ true, $$ r $$ false. Original: false implies (true or false) = false implies true = true. Option A: $$ (\text{false} \vee \text{true}) \Rightarrow \text{false} = \text{true} \Rightarrow \text{false} = \text{false} $$. Not the same. So, not equivalent.
Option B: $$ (p \Rightarrow q) \vee (p \Rightarrow r) $$
Rewrite each implication:
$$ p \Rightarrow q = \sim p \vee q $$
$$ p \Rightarrow r = \sim p \vee r $$
So the expression becomes:
$$ (\sim p \vee q) \vee (\sim p \vee r) $$
Since disjunction is associative and commutative, rearrange:
$$ \sim p \vee \sim p \vee q \vee r $$
Simplify ($$ \sim p \vee \sim p = \sim p $$):
$$ \sim p \vee q \vee r $$
This matches the original expression exactly. So, option B is equivalent.
Option C: $$ (p \Rightarrow \sim q) \wedge (p \Rightarrow r) $$
Rewrite each implication:
$$ p \Rightarrow \sim q = \sim p \vee \sim q $$
$$ p \Rightarrow r = \sim p \vee r $$
So the expression is:
$$ (\sim p \vee \sim q) \wedge (\sim p \vee r) $$
Factor out $$ \sim p $$ using distribution:
$$ \sim p \vee (\sim q \wedge r) $$
This is not the same as $$ \sim p \vee q \vee r $$. For example, if $$ p $$ is true, $$ q $$ is true, and $$ r $$ is false, the original statement is true (true implies (true or false) = true implies true = true), but this expression is $$ \text{false} \vee (\text{false} \wedge \text{false}) = \text{false} \vee \text{false} = \text{false} $$. Not equivalent.
Option D: $$ (p \Rightarrow q) \wedge (p \Rightarrow \sim r) $$
Rewrite each implication:
$$ p \Rightarrow q = \sim p \vee q $$
$$ p \Rightarrow \sim r = \sim p \vee \sim r $$
So the expression is:
$$ (\sim p \vee q) \wedge (\sim p \vee \sim r) $$
Factor out $$ \sim p $$:
$$ \sim p \vee (q \wedge \sim r) $$
This is not the same as $$ \sim p \vee q \vee r $$. For example, if $$ p $$ is true, $$ q $$ is false, and $$ r $$ is true, the original statement is true (true implies (false or true) = true implies true = true), but this expression is $$ \text{false} \vee (\text{false} \wedge \text{false}) = \text{false} \vee \text{false} = \text{false} $$. Not equivalent.
Therefore, only option B is logically equivalent to the given statement. Hence, the correct answer is Option B.
The statement $$\sim(p \leftrightarrow \sim q)$$ is:
We have to examine the statement $$\sim\!\left(p \leftrightarrow \sim q\right)$$ and decide which description among the four alternatives fits it.
First, recall the standard logical equivalence formula for a biconditional. We state it explicitly:
$$p \leftrightarrow r \;\equiv\; (p \wedge r)\;\vee\;(\sim p \wedge \sim r).$$
The symbol “$$\equiv$$” means “is logically equivalent to.” In our problem the role of $$r$$ is played by $$\sim q$$, so we substitute $$r = \sim q$$:
$$p \leftrightarrow \sim q \;\equiv\; \bigl(p \wedge \sim q\bigr)\;\vee\;\bigl(\sim p \wedge \sim(\sim q)\bigr).$$
Because a double negation cancels, $$\sim(\sim q)=q$$. Substituting this, we simplify the right-hand side:
$$p \leftrightarrow \sim q \;\equiv\; \bigl(p \wedge \sim q\bigr)\;\vee\;\bigl(\sim p \wedge q\bigr).$$
Now our original expression contains the negation of this whole biconditional, so we negate what we have just obtained:
$$\sim\!\left(p \leftrightarrow \sim q\right) \;\equiv\; \sim\!\Bigl[\, \bigl(p \wedge \sim q\bigr)\;\vee\;\bigl(\sim p \wedge q\bigr)\Bigr].$$
Next we invoke De Morgan’s law, which states
$$\sim(A \vee B) \;\equiv\; (\sim A) \wedge (\sim B).$$
Identifying $$A = (p \wedge \sim q)$$ and $$B = (\sim p \wedge q)$$, we apply the law:
$$\sim\!\left(p \leftrightarrow \sim q\right) \;\equiv\; \bigl(\sim(p \wedge \sim q)\bigr)\;\wedge\;\bigl(\sim(\sim p \wedge q)\bigr).$$
Each of the two negations inside the brackets can again be opened with De Morgan’s law, this time in its conjunctive form
$$\sim(X \wedge Y) \;\equiv\; (\sim X) \vee (\sim Y).$$
For the first bracket we have $$X=p$$ and $$Y=\sim q$$, giving
$$\sim(p \wedge \sim q) \;\equiv\; (\sim p) \vee \bigl(\sim(\sim q)\bigr).$$
The double negation $$\sim(\sim q)$$ collapses to $$q$$, so the first bracket becomes
$$\sim(p \wedge \sim q) \;\equiv\; (\sim p) \vee q.$$
For the second bracket we have $$X=\sim p$$ and $$Y=q$$, yielding
$$\sim(\sim p \wedge q) \;\equiv\; \bigl(\sim(\sim p)\bigr) \vee (\sim q).$$
Again the double negation $$\sim(\sim p)$$ reduces to $$p$$, giving
$$\sim(\sim p \wedge q) \;\equiv\; p \vee (\sim q).$$
Collecting both results, we have transformed the original statement into
$$\sim\!\left(p \leftrightarrow \sim q\right) \;\equiv\; \bigl((\sim p) \vee q\bigr)\;\wedge\;\bigl(p \vee (\sim q)\bigr).$$
Thus
$$\boxed{\; \sim\!\left(p \leftrightarrow \sim q\right) \;\equiv\; (\sim p \vee q)\;\wedge\;(p \vee \sim q) \;}$$
We now show that the right-hand side is exactly $$p \leftrightarrow q$$. To see this, we once more recall the biconditional formula, this time with $$r=q$$:
$$p \leftrightarrow q \;\equiv\; (p \wedge q)\;\vee\;(\sim p \wedge \sim q).$$
One way to verify equivalence of two compound statements is to check that their truth tables match. Below are the four possible truth-value assignments for $$p$$ and $$q$$, and the resulting truth values of $$(\sim p \vee q)\wedge(p \vee \sim q)$$:
$$ \begin{array}{c|c||c|c|c} p & q & \sim p \vee q & p \vee \sim q & \text{Conjunction} \\ \hline T & T & T & T & T\\ T & F & F & T & F\\ F & T & T & F & F\\ F & F & T & T & T \end{array} $$
The last column reads T, F, F, T—precisely the truth pattern of $$p \leftrightarrow q$$. Hence
$$ (\sim p \vee q)\;\wedge\;(p \vee \sim q) \;\equiv\; p \leftrightarrow q. $$
Combining this with the boxed equivalence obtained earlier, we finally deduce
$$\boxed{\; \sim\!\left(p \leftrightarrow \sim q\right) \;\equiv\; p \leftrightarrow q \;}$$
This matches Option C in the given list. It is therefore neither a tautology nor a fallacy in isolation; it is simply equivalent to another specific biconditional.
Hence, the correct answer is Option C.
The proposition $$\sim (p \vee \sim q) \vee \sim (p \vee q)$$ is logically equivalent to:
We start with the proposition: $$\sim (p \vee \sim q) \vee \sim (p \vee q)$$.
First, apply De Morgan's law to both parts. De Morgan's law states that $$\sim (A \vee B) = (\sim A) \wedge (\sim B)$$.
For the left part: $$\sim (p \vee \sim q)$$. Here, $$A = p$$ and $$B = \sim q$$, so:
$$\sim (p \vee \sim q) = (\sim p) \wedge \sim(\sim q)$$.
Since $$\sim(\sim q) = q$$, this simplifies to:
$$(\sim p) \wedge q$$.
For the right part: $$\sim (p \vee q)$$. Here, $$A = p$$ and $$B = q$$, so:
$$\sim (p \vee q) = (\sim p) \wedge (\sim q)$$.
Now the expression becomes:
$$(\sim p \wedge q) \vee (\sim p \wedge \sim q)$$.
Notice that $$\sim p$$ is common in both terms. Factor out $$\sim p$$:
$$\sim p \wedge (q \vee \sim q)$$.
We know that $$q \vee \sim q$$ is always true (tautology), because either $$q$$ is true or false. So:
$$q \vee \sim q = \text{True}$$.
Substitute this back:
$$\sim p \wedge \text{True}$$.
Any proposition AND True is the proposition itself. Therefore:
$$\sim p \wedge \text{True} = \sim p$$.
So, the original proposition simplifies to $$\sim p$$.
Comparing with the options:
A. p
B. q
C. $$\sim p$$
D. $$\sim q$$
Hence, the correct answer is Option C.
The contrapositive of the statement "I go to school if it does not rain" is:
If $$X = \{4^n - 3n - 1 : n \in N\}$$ and $$Y = \{9(n-1) : n \in N\}$$, where $$N$$ is the set of natural numbers, then $$X \cup Y$$ is equal to:
We have two sets of natural-number valued expressions
$$X=\{\,4^{\,n}-3n-1 : n\in N\,\} \quad\text{and}\quad Y=\{\,9(n-1) : n\in N\,\},$$ where $$N=\{1,2,3,\dots\}.$$
Our task is to identify the union $$X\cup Y.$$ To do this we shall show that every element of $$X$$ is already present in $$Y.$$ If that is true then $$X\subseteq Y,$$ and consequently $$X\cup Y=Y.$$
For any natural number $$n,$$ consider the expression
$$4^{\,n}-3n-1.$$
We want to see whether this number is a multiple of $$9.$$ A convenient way to check divisibility by $$9$$ is to look at the remainder (the “modulus”) of the number when divided by $$9.$$ Hence we examine $$4^{\,n}\pmod 9.$$
First, note that
$$4\equiv 4\pmod 9,$$
$$4^{\,2}=16\equiv 7\pmod 9,$$
$$4^{\,3}=64\equiv 1\pmod 9.$$
The remainders repeat every three powers because $$4^{\,3}=1\pmod 9\;\Longrightarrow\;4^{\,3k}=1\pmod 9,$$ and multiplying by another $$4$$ or $$4^{\,2}$$ gives the other two remainders. So we have the periodic pattern
$$4^{\,n}\equiv \begin{cases} 4,& n\equiv 1\pmod 3,\\[6pt] 7,& n\equiv 2\pmod 3,\\[6pt] 1,& n\equiv 0\pmod 3. \end{cases}$$
Now write $$n=3k,\,3k+1,$$ or $$3k+2,$$ and compute the whole expression modulo $$9$$ in each case.
1. If $$n=3k,$$ then $$4^{\,n}\equiv 1.$$ So
$$4^{\,n}-3n-1 =1-3(3k)-1 =1-9k-1 =-9k \equiv 0\pmod 9.$$
2. If $$n=3k+1,$$ then $$4^{\,n}\equiv 4.$$ So
$$4^{\,n}-3n-1 =4-3(3k+1)-1 =4-9k-3-1 =-9k \equiv 0\pmod 9.$$
3. If $$n=3k+2,$$ then $$4^{\,n}\equiv 7.$$ So
$$4^{\,n}-3n-1 =7-3(3k+2)-1 =7-9k-6-1 =-9k \equiv 0\pmod 9.$$
In every case the remainder is zero, so
$$9\;\big\vert\;\bigl(4^{\,n}-3n-1\bigr).$$
Therefore, for each $$n\in N$$ there exists some non-negative integer $$m$$ such that
$$4^{\,n}-3n-1=9m.$$
But the set $$Y=\{9(n-1):n\in N\}$$ contains every non-negative multiple of $$9$$ (namely $$0,9,18,27,\dots$$). Hence the number $$9m$$ we obtained is automatically an element of $$Y.$$ So we have proved
$$X\subseteq Y.$$
Because the union of a set with its superset is the superset itself, we now have
$$X\cup Y=Y.$$
Thus the union equals $$Y,$$ which corresponds to Option B.
Hence, the correct answer is Option B.
Let $$P$$ be the relation defined on the set of all real numbers such that $$P = \{(a, b) : \sec^2 a - \tan^2 b = 1\}$$. Then, $$P$$ is:
The relation $$P$$ is defined on the set of all real numbers as $$P = \{(a, b) : \sec^2 a - \tan^2 b = 1\}$$. However, $$\sec a$$ and $$\tan b$$ are undefined when $$a$$ or $$b$$ is an odd multiple of $$\pi/2$$, i.e., $$a = (2k+1)\pi/2$$ or $$b = (2k+1)\pi/2$$ for any integer $$k$$. Therefore, the domain $$D$$ for which the relation is defined consists of all real numbers except these points. We will check the properties of reflexivity, symmetry, and transitivity for $$P$$ on this domain $$D$$.
Reflexivity: A relation is reflexive if for every $$a$$ in the domain, $$(a, a)$$ is in $$P$$. For any $$a \in D$$, we need to check if $$\sec^2 a - \tan^2 a = 1$$. Using the trigonometric identity $$\sec^2 \theta - \tan^2 \theta = 1$$, which holds for all $$\theta$$ where both functions are defined, we have $$\sec^2 a - \tan^2 a = 1$$. Thus, $$(a, a) \in P$$ for all $$a \in D$$. Therefore, $$P$$ is reflexive.
Symmetry: A relation is symmetric if whenever $$(a, b) \in P$$, then $$(b, a) \in P$$. Assume $$(a, b) \in P$$, so $$\sec^2 a - \tan^2 b = 1$$. We need to show that $$\sec^2 b - \tan^2 a = 1$$. From the given condition, $$\sec^2 a - \tan^2 b = 1$$. Rearranging, $$\sec^2 a = 1 + \tan^2 b$$. Using the identity $$\sec^2 b = 1 + \tan^2 b$$, we substitute to get $$\sec^2 b = 1 + \tan^2 b$$. Similarly, $$\tan^2 a = \sec^2 a - 1 = (1 + \tan^2 b) - 1 = \tan^2 b$$. Now, $$\sec^2 b - \tan^2 a = (1 + \tan^2 b) - \tan^2 a$$. Since $$\tan^2 a = \tan^2 b$$, this becomes $$1 + \tan^2 b - \tan^2 b = 1$$. Thus, $$\sec^2 b - \tan^2 a = 1$$, so $$(b, a) \in P$$. Therefore, $$P$$ is symmetric.
Transitivity: A relation is transitive if whenever $$(a, b) \in P$$ and $$(b, c) \in P$$, then $$(a, c) \in P$$. Assume $$(a, b) \in P$$ and $$(b, c) \in P$$, so $$\sec^2 a - \tan^2 b = 1$$ and $$\sec^2 b - \tan^2 c = 1$$. We need to show $$\sec^2 a - \tan^2 c = 1$$. From $$(a, b) \in P$$, $$\sec^2 a - \tan^2 b = 1$$, so $$\sec^2 a = 1 + \tan^2 b$$. From $$(b, c) \in P$$, $$\sec^2 b - \tan^2 c = 1$$, so $$\tan^2 c = \sec^2 b - 1$$. Now, $$\sec^2 a - \tan^2 c = (1 + \tan^2 b) - (\sec^2 b - 1)$$. Since $$\sec^2 b = 1 + \tan^2 b$$, substitute to get $$\sec^2 a - \tan^2 c = 1 + \tan^2 b - [(1 + \tan^2 b) - 1] = 1 + \tan^2 b - [\tan^2 b] = 1$$. Thus, $$\sec^2 a - \tan^2 c = 1$$, so $$(a, c) \in P$$. Therefore, $$P$$ is transitive.
Since $$P$$ is reflexive, symmetric, and transitive on its domain, it is an equivalence relation.
Hence, the correct answer is Option D.
Let $$f : R \to R$$ be defined by $$f(x) = \frac{|x|-1}{|x|+1}$$, then f is:
We are given a function $$ f : \mathbb{R} \to \mathbb{R} $$ defined by $$ f(x) = \frac{|x| - 1}{|x| + 1} $$. We need to determine if this function is one-one (injective), onto (surjective), both, or neither. A function is one-one if different inputs always give different outputs, meaning if $$ f(a) = f(b) $$, then $$ a = b $$. A function is onto if every element in the codomain is mapped to by some element in the domain, meaning for every real number $$ y $$, there exists some $$ x $$ such that $$ f(x) = y $$. The codomain here is all real numbers, $$ \mathbb{R} $$.
First, we check if the function is one-one. Notice that the expression depends on $$ |x| $$, which is always non-negative. For any $$ x $$, $$ |x| = |-x| $$, so let us compute $$ f(-x) $$:
$$ f(-x) = \frac{|-x| - 1}{|-x| + 1} = \frac{|x| - 1}{|x| + 1} = f(x). $$
This shows that $$ f(-x) = f(x) $$ for all $$ x $$. Therefore, for any $$ x \neq 0 $$, we have $$ f(x) = f(-x) $$, but $$ x $$ and $$ -x $$ are different if $$ x \neq 0 $$. For example, let $$ x = 1 $$:
$$ f(1) = \frac{|1| - 1}{|1| + 1} = \frac{1 - 1}{1 + 1} = \frac{0}{2} = 0. $$
Now, $$ f(-1) = \frac{|-1| - 1}{|-1| + 1} = \frac{1 - 1}{1 + 1} = \frac{0}{2} = 0 $$. So $$ f(1) = f(-1) = 0 $$, but $$ 1 \neq -1 $$. Since two different inputs ($$ 1 $$ and $$ -1 $$) give the same output ($$ 0 $$), the function is not one-one.
Next, we check if the function is onto. To be onto, for every real number $$ y $$, there must be some $$ x $$ such that $$ f(x) = y $$. Since $$ f(x) $$ depends only on $$ |x| $$, we set $$ t = |x| \geq 0 $$. Then the function becomes:
$$ g(t) = \frac{t - 1}{t + 1}, \quad t \geq 0. $$
We need to find the range of $$ g(t) $$ as $$ t $$ varies from 0 to infinity. This range will be the same as the range of $$ f(x) $$, because for each $$ t \geq 0 $$, there is at least one $$ x $$ (for example, $$ x = t $$ or $$ x = -t $$) such that $$ |x| = t $$.
Evaluate $$ g(t) $$ at key points:
- When $$ t = 0 $$: $$ g(0) = \frac{0 - 1}{0 + 1} = \frac{-1}{1} = -1 $$.
- When $$ t = 1 $$: $$ g(1) = \frac{1 - 1}{1 + 1} = \frac{0}{2} = 0 $$.
- As $$ t \to \infty $$: $$ g(t) = \frac{t - 1}{t + 1} = \frac{1 - \frac{1}{t}}{1 + \frac{1}{t}} \to \frac{1 - 0}{1 + 0} = 1 $$.
Now, check if $$ g(t) $$ can equal 1: set $$ \frac{t - 1}{t + 1} = 1 $$. Then $$ t - 1 = t + 1 $$, which simplifies to $$ -1 = 1 $$, a contradiction. So $$ g(t) \neq 1 $$ for any $$ t \geq 0 $$.
To see how $$ g(t) $$ behaves, compute its derivative. Let $$ g(t) = \frac{t - 1}{t + 1} $$. Using the quotient rule:
$$ g'(t) = \frac{(1)(t + 1) - (t - 1)(1)}{(t + 1)^2} = \frac{t + 1 - (t - 1)}{(t + 1)^2} = \frac{t + 1 - t + 1}{(t + 1)^2} = \frac{2}{(t + 1)^2}. $$
Since $$ (t + 1)^2 > 0 $$ for all $$ t \geq 0 $$, we have $$ g'(t) > 0 $$, so $$ g(t) $$ is strictly increasing for $$ t \geq 0 $$.
As $$ t $$ increases from 0 to infinity, $$ g(t) $$ increases continuously from $$ g(0) = -1 $$ to the limit 1 (but never reaches 1). Therefore, the range of $$ g(t) $$ is all real numbers from -1 inclusive to 1 exclusive, denoted as $$ [-1, 1) $$.
Since $$ f(x) $$ has the same range $$ [-1, 1) $$, we can see that:
- $$ y = -1 $$ is achieved when $$ x = 0 $$ (since $$ f(0) = \frac{|0| - 1}{|0| + 1} = \frac{-1}{1} = -1 $$).
- Values between -1 and 1 are achieved; for example, for $$ y = 0.5 $$, solve $$ \frac{t - 1}{t + 1} = 0.5 $$: $$ t - 1 = 0.5(t + 1) \implies t - 1 = 0.5t + 0.5 \implies t - 0.5t = 0.5 + 1 \implies 0.5t = 1.5 \implies t = 3. $$ So $$ |x| = 3 $$, meaning $$ x = 3 $$ or $$ x = -3 $$, and $$ f(3) = \frac{|3| - 1}{|3| + 1} = \frac{3 - 1}{3 + 1} = \frac{2}{4} = 0.5 $$.
- But $$ y = 1 $$ is not achieved, as shown earlier.
Now, consider values outside $$ [-1, 1) $$. For example, $$ y = 2 $$:
Set $$ f(x) = 2 $$: $$ \frac{|x| - 1}{|x| + 1} = 2 \implies |x| - 1 = 2(|x| + 1) \implies |x| - 1 = 2|x| + 2 \implies -1 - 2 = 2|x| - |x| \implies -3 = |x| $$. But $$ |x| \geq 0 $$, so $$ |x| = -3 $$ is impossible. Similarly, for $$ y = -2 $$: $$ \frac{|x| - 1}{|x| + 1} = -2 \implies |x| - 1 = -2(|x| + 1) \implies |x| - 1 = -2|x| - 2 \implies |x| + 2|x| = -2 + 1 \implies 3|x| = -1 $$, again impossible.
Thus, the range of $$ f $$ is $$ [-1, 1) $$, which is a proper subset of the codomain $$ \mathbb{R} $$. For instance, $$ y = 1 $$ and $$ y = 2 $$ are in $$ \mathbb{R} $$ but not in the range. Therefore, $$ f $$ is not onto.
Since $$ f $$ is not one-one and not onto, it is neither injective nor surjective.
Hence, the correct answer is Option B.
Let $$p$$ and $$q$$ be any two logical statements and $$r : p \rightarrow (\sim p \vee q)$$. If $$r$$ has a truth value $$F$$, then the truth values of $$p$$ and $$q$$ are respectively:
We are given that $$ r: p \rightarrow (\sim p \vee q) $$ has a truth value of false (F). We need to find the truth values of $$ p $$ and $$ q $$ that make $$ r $$ false.
Recall that an implication $$ a \rightarrow b $$ is false only when $$ a $$ is true and $$ b $$ is false. For $$ r $$ to be false, we must have:
- $$ p $$ is true (T), and
- $$ \sim p \vee q $$ is false (F).
Now, a disjunction (OR) like $$ \sim p \vee q $$ is false only when both components are false. Therefore:
- $$ \sim p $$ must be false (F), and
- $$ q $$ must be false (F).
If $$ \sim p $$ is false, then $$ p $$ must be true (T), because the negation of true is false and vice versa. This matches the first condition that $$ p $$ is true.
Thus, we have:
- $$ p = \text{T} $$
- $$ q = \text{F} $$
Let us verify these truth values by substituting them into $$ r $$.
If $$ p $$ is true (T), then $$ \sim p $$ is false (F).
Now, $$ \sim p \vee q = \text{F} \vee \text{F} = \text{F} $$ (since both are false).
Then, $$ r: p \rightarrow (\sim p \vee q) = \text{T} \rightarrow \text{F} $$.
We know that true implies false is false (T → F = F), which matches the given condition that $$ r $$ is false.
Therefore, the truth values of $$ p $$ and $$ q $$ are true (T) and false (F) respectively.
Looking at the options:
- A. F, F
- B. T, T
- C. T, F
- D. F, T
Option C matches T, F.
Hence, the correct answer is Option C.
The statement $$p \rightarrow (q \rightarrow p)$$ is equivalent to :
We are given the statement $$ p \rightarrow (q \rightarrow p) $$ and need to find which option it is equivalent to. Recall that the implication $$ a \rightarrow b $$ is logically equivalent to $$ \neg a \vee b $$. We will use this equivalence to simplify the given statement step by step.
First, consider the inner implication $$ q \rightarrow p $$. Using the equivalence, we rewrite it as $$ \neg q \vee p $$. So the entire statement becomes:
$$ p \rightarrow (\neg q \vee p) $$
Now, apply the equivalence to the outer implication $$ p \rightarrow (\neg q \vee p) $$. This becomes:
$$ \neg p \vee (\neg q \vee p) $$
Disjunction (OR) is associative, meaning we can regroup the terms without changing the meaning. So we write:
$$ (\neg p \vee p) \vee \neg q $$
Notice that $$ \neg p \vee p $$ is a tautology, meaning it is always true, regardless of the truth value of $$ p $$. Therefore:
$$ \neg p \vee p = \text{true} $$
Substituting this, we get:
$$ \text{true} \vee \neg q $$
The disjunction of true and any statement is always true. So:
$$ \text{true} \vee \neg q = \text{true} $$
Thus, the original statement $$ p \rightarrow (q \rightarrow p) $$ simplifies to true, meaning it is a tautology (always true).
Now, we check each option to see which one is also a tautology and equivalent to true.
Option A: $$ p \rightarrow q $$
Rewrite using equivalence:
$$ \neg p \vee q $$
This is not always true. For example, when $$ p $$ is true and $$ q $$ is false, $$ \neg p \vee q = \text{false} \vee \text{false} = \text{false} $$. So it is not a tautology and not equivalent to the original statement.
Option B: $$ p \rightarrow (p \vee q) $$
Rewrite using equivalence:
$$ \neg p \vee (p \vee q) $$
Associativity allows regrouping:
$$ (\neg p \vee p) \vee q $$
Again, $$ \neg p \vee p = \text{true} $$, so:
$$ \text{true} \vee q = \text{true} $$
This is a tautology. Therefore, it is equivalent to the original statement.
Option C: $$ p \rightarrow (p \rightarrow q) $$
First, rewrite the inner implication $$ p \rightarrow q $$ as $$ \neg p \vee q $$. So the statement becomes:
$$ p \rightarrow (\neg p \vee q) $$
Apply equivalence to the outer implication:
$$ \neg p \vee (\neg p \vee q) $$
Associativity and idempotence (since $$ \neg p \vee \neg p = \neg p $$):
$$ (\neg p \vee \neg p) \vee q = \neg p \vee q $$
This is $$ \neg p \vee q $$, which is the same as $$ p \rightarrow q $$. As in Option A, this is not a tautology (e.g., false when $$ p $$ is true and $$ q $$ is false). So it is not equivalent to the original statement.
Option D: $$ p \rightarrow (p \wedge q) $$
Rewrite using equivalence:
$$ \neg p \vee (p \wedge q) $$
Distribute $$ \vee $$ over $$ \wedge $$:
$$ (\neg p \vee p) \wedge (\neg p \vee q) $$
Now, $$ \neg p \vee p = \text{true} $$, so:
$$ \text{true} \wedge (\neg p \vee q) = \neg p \vee q $$
Again, this is $$ \neg p \vee q $$, same as $$ p \rightarrow q $$, which is not a tautology. So it is not equivalent to the original statement.
Only Option B simplifies to true, making it a tautology and equivalent to the original statement $$ p \rightarrow (q \rightarrow p) $$.
Hence, the correct answer is Option B.
Consider :
Statement - I : $$(p \wedge \sim q) \wedge (\sim p \wedge q)$$ is a fallacy.
Statement - II : $$(p \rightarrow q) \leftrightarrow (\sim q \rightarrow \sim p)$$ is a tautology.
First we recall some basic logical equivalences that we shall use again and again.
Implication : $$\, (A \rightarrow B)\; \equiv\; (\sim A)\,\vee\,B \,.$$ Biconditional : $$\, (X \leftrightarrow Y)\; \equiv\; (X \wedge Y)\,\vee\,(\sim X \wedge \sim Y)\;.$$ Associative and commutative laws allow us to rearrange and regroup the symbols $$\wedge$$ and $$\vee$$ freely.
Now we examine Statement I :
We have $$ (p \wedge \sim q) \wedge (\sim p \wedge q). $$ Because the conjunction $$\wedge$$ is associative, the brackets may be dropped one at a time:
$$ (p \wedge \sim q) \wedge (\sim p \wedge q) \;=\; p \wedge \sim q \wedge \sim p \wedge q. $$
Next, with the commutative law we collect like symbols together:
$$ p \wedge \sim p \wedge \sim q \wedge q. $$
Inside the expression we clearly see $$p \wedge \sim p$$ and also $$q \wedge \sim q$$. Each of these pairs is always false because a statement and its negation can never be true simultaneously. Hence
$$ p \wedge \sim p \;=\; \text{False}, \qquad q \wedge \sim q \;=\; \text{False}. $$
So the whole conjunction becomes
$$ \text{False} \wedge \text{False} \;=\; \text{False}. $$
The result does not depend on the particular truth-values of $$p$$ or $$q$$; it is always false. A statement that is always false is called a fallacy. Therefore Statement I is true.
Next we analyse Statement II :
We start with the given biconditional $$ (p \rightarrow q) \leftrightarrow (\sim q \rightarrow \sim p). $$
Using the implication formula quoted at the beginning, we transform each part separately.
First, $$ p \rightarrow q \;\equiv\; \sim p \,\vee\, q. $$
Second, we handle the contrapositive implication carefully. Applying $$(A \rightarrow B) \equiv (\sim A) \vee B$$ with $$A = \sim q$$ and $$B = \sim p$$ we obtain
$$ \sim q \rightarrow \sim p \;\equiv\; \sim(\sim q) \,\vee\, \sim p \;=\; q \,\vee\, \sim p. $$
Notice that the disjunction $$q \vee \sim p$$ is identical to $$\sim p \vee q$$ because $$\vee$$ is commutative. Hence we can write
$$ q \vee \sim p \;=\; \sim p \vee q. $$
So both sides of the biconditional are in fact the same formula:
$$ (p \rightarrow q) \;\equiv\; \sim p \vee q, $$ $$ (\sim q \rightarrow \sim p) \;\equiv\; \sim p \vee q. $$
Therefore the whole statement becomes
$$ (\sim p \vee q) \leftrightarrow (\sim p \vee q). $$
A biconditional of any statement with itself, i.e. $$X \leftrightarrow X,$$ is always true, because both possible parts in the definition $$(X \wedge X) \vee (\sim X \wedge \sim X)$$ are automatically satisfied. Hence the biconditional above is always true; that is, it is a tautology. So Statement II is also true.
We must still decide whether Statement II provides a correct explanation for Statement I. Statement II merely tells us that an implication is equivalent to its contrapositive; it does not explain why the particular conjunction in Statement I is always false. Thus, while both statements are true, Statement II is not the reason for Statement I.
The situation matches Option D.
Hence, the correct answer is Option D.
Statement-1: The statement $$A \rightarrow (B \rightarrow A)$$ is equivalent to $$A \rightarrow (A \vee B)$$.
Statement-2: The statement $$\sim [(A \wedge B) \rightarrow (\sim A \vee B)]$$ is a Tautology.
We are given two statements and need to evaluate their truth values and the relationship between them. The options are based on whether each statement is true or false and if Statement-2 explains Statement-1.
First, we address Statement-1: The statement $$A \rightarrow (B \rightarrow A)$$ is equivalent to $$A \rightarrow (A \vee B)$$. Two statements are equivalent if they have the same truth value for all possible truth values of their variables. We will use truth tables to verify this.
Construct a truth table for both expressions. Since there are two variables, A and B, there are four combinations of truth values.
For $$A \rightarrow (B \rightarrow A)$$:
- Implication $$P \rightarrow Q$$ is false only when P is true and Q is false; otherwise, it is true.
- $$B \rightarrow A$$ is equivalent to $$\neg B \vee A$$.
For $$A \rightarrow (A \vee B)$$:
- $$A \vee B$$ is false only when both A and B are false; otherwise, it is true.
The truth table is as follows:
| A | B | B → A | A ∨ B | A → (B → A) | A → (A ∨ B) |
|---|---|---|---|---|---|
| T | T | T → T = T | T ∨ T = T | T → T = T | T → T = T |
| T | F | F → T = T | T ∨ F = T | T → T = T | T → T = T |
| F | T | T → F = F | F ∨ T = T | F → F = T | F → T = T |
| F | F | F → F = T | F ∨ F = F | F → T = T | F → F = T |
In all rows, both expressions evaluate to true. Therefore, $$A \rightarrow (B \rightarrow A)$$ and $$A \rightarrow (A \vee B)$$ are both tautologies and hence equivalent. So, Statement-1 is true.
Now, we address Statement-2: The statement $$\sim [(A \wedge B) \rightarrow (\sim A \vee B)]$$ is a tautology. A tautology is a statement that is always true, regardless of the truth values of its variables.
We simplify the given expression step by step:
- Recall that $$P \rightarrow Q$$ is equivalent to $$\neg P \vee Q$$.
- So, $$(A \wedge B) \rightarrow (\sim A \vee B)$$ is equivalent to $$\neg (A \wedge B) \vee (\sim A \vee B)$$.
- The negation of the implication is $$\sim [(A \wedge B) \rightarrow (\sim A \vee B)] = \sim [\neg (A \wedge B) \vee (\sim A \vee B)]$$.
- By De Morgan's law, $$\sim [\neg (A \wedge B) \vee (\sim A \vee B)] = (A \wedge B) \wedge \sim (\sim A \vee B)$$.
- Now, $$\sim (\sim A \vee B) = \sim (\sim A) \wedge \sim B = A \wedge \sim B$$ (by De Morgan's law).
- So, the expression becomes $$(A \wedge B) \wedge (A \wedge \sim B)$$.
- Simplify: $$(A \wedge B) \wedge (A \wedge \sim B) = A \wedge A \wedge B \wedge \sim B = A \wedge (B \wedge \sim B) = A \wedge \text{false} = \text{false}$$.
The expression simplifies to false, which is a contradiction (always false). Therefore, it cannot be a tautology. So, Statement-2 is false.
We can also verify with a truth table:
| A | B | A ∧ B | ∼A | ∼A ∨ B | (A ∧ B) → (∼A ∨ B) | ∼[(A ∧ B) → (∼A ∨ B)] |
|---|---|---|---|---|---|---|
| T | T | T | F | T | T → T = T | ∼T = F |
| T | F | F | F | F | F → F = T | ∼T = F |
| F | T | F | T | T | F → T = T | ∼T = F |
| F | F | F | T | T | F → T = T | ∼T = F |
In every row, the expression $$\sim [(A \wedge B) \rightarrow (\sim A \vee B)]$$ is false. Hence, it is a contradiction, not a tautology. Thus, Statement-2 is false.
Now, evaluating the options:
- Option A: Statement-1 false; Statement-2 true → Incorrect, as Statement-1 is true and Statement-2 is false.
- Option B: Both true; Statement-2 not correct explanation → Incorrect, as Statement-2 is false.
- Option C: Statement-1 true; Statement-2 false → Correct.
- Option D: Both true; Statement-2 correct explanation → Incorrect, as Statement-2 is false.
Hence, the correct answer is Option C.
Let $$A = \{1, 2, 3, 4\}$$ and $$R : A \rightarrow A$$ be the relation defined by $$R = \{(1,1), (2,3), (3,4), (4,2)\}$$. The correct statement is :
First, we need to check if the relation $$R$$ is a function. A relation from set $$A$$ to set $$A$$ is a function if every element in the domain $$A$$ is mapped to exactly one element in the codomain $$A$$. Here, $$A = \{1, 2, 3, 4\}$$ and $$R = \{(1,1), (2,3), (3,4), (4,2)\}$$.
Examine each element of $$A$$:
For element 1, the pair $$(1,1)$$ maps it to 1, so $$R(1) = 1$$.
For element 2, the pair $$(2,3)$$ maps it to 3, so $$R(2) = 3$$.
For element 3, the pair $$(3,4)$$ maps it to 4, so $$R(3) = 4$$.
For element 4, the pair $$(4,2)$$ maps it to 2, so $$R(4) = 2$$.
Since every element in $$A$$ has exactly one image in $$A$$, $$R$$ is a function. Therefore, option D, which states "R is not a function," is incorrect.
Next, we check if $$R$$ is one-to-one (injective). A function is one-to-one if different inputs produce different outputs, meaning if $$R(a) = R(b)$$, then $$a = b$$.
List the outputs:
$$R(1) = 1$$, $$R(2) = 3$$, $$R(3) = 4$$, $$R(4) = 2$$.
The outputs are 1, 3, 4, and 2, all distinct. Since no two different inputs share the same output, $$R$$ is one-to-one. Therefore, option B, which states "R is not a one to one function," is incorrect.
Now, check if $$R$$ is onto (surjective). A function is onto if every element in the codomain is mapped to by some element in the domain. The codomain is $$A = \{1, 2, 3, 4\}$$.
Check each element:
Is 1 mapped to? Yes, because $$R(1) = 1$$, so 1 is the image of 1.
Is 2 mapped to? Yes, because $$R(4) = 2$$, so 2 is the image of 4.
Is 3 mapped to? Yes, because $$R(2) = 3$$, so 3 is the image of 2.
Is 4 mapped to? Yes, because $$R(3) = 4$$, so 4 is the image of 3.
Since every element in the codomain $$A$$ is an image of some element in the domain, $$R$$ is onto. Therefore, option C, which states "R is an onto function," is correct.
To address option A, since $$R$$ is both one-to-one and onto, it is bijective. A bijective function has an inverse. The inverse function $$R^{-1}$$ can be found by swapping the pairs: $$R^{-1} = \{(1,1), (3,2), (4,3), (2,4)\}$$, which is equivalent to $$R^{-1}(1) = 1$$, $$R^{-1}(2) = 4$$, $$R^{-1}(3) = 2$$, $$R^{-1}(4) = 3$$. This is a valid function, so $$R$$ has an inverse. Therefore, option A, which states "R does not have an inverse," is incorrect.
Hence, the correct answer is Option C.
The logically equivalent proposition of $$p \Leftrightarrow q$$ is
Using definition of biconditional equivalence:
$$p \iff q \equiv (p \implies q) \wedge (q \implies p)$$
Let $$p$$ and $$q$$ be two Statements. Amongst the following, the Statement that is equivalent to $$p \to q$$ is
The negation of the statement "If I become a teacher, then I will open a school" is
The Statement that is TRUE among the following is
Let $$p$$ and $$q$$ denote the following statements $$p$$: The sun is shining; $$q$$: I shall play tennis in the afternoon. The negation of the statement "If the sun is shining then I shall play tennis in the afternoon", is
Let $$A$$ and $$B$$ be non empty sets in $$R$$ and $$f : A \to B$$ is a bijective function. Statement 1: $$f$$ is an onto function. Statement 2: There exists a function $$g : B \to A$$ such that $$f \circ g = I_B$$.
The problem gives a bijective map $$f : A \rightarrow B$$ between two non-empty subsets of $$\mathbb{R}$$ and asks us to compare two statements.
Statement 1: “$$f$$ is an onto (surjective) function.”
Statement 2: “There exists a function $$g : B \rightarrow A$$ such that $$f \circ g = I_B$$ (the identity map on $$B$$).”
Recall the definitions first.
• A function is called bijective when it is both one-one (injective) and onto (surjective).
• A function $$g : B \rightarrow A$$ satisfying $$f\circ g = I_B$$ is called a right inverse of $$f$$. A right inverse exists precisely when $$f$$ is surjective.
Now check the two statements one by one.
Step 1: Truth of Statement 1
Since $$f$$ is given to be bijective, surjectivity is already included in the definition. Therefore $$f$$ is indeed onto. Statement 1 is true.
Step 2: Truth of Statement 2
For each $$y\in B$$, surjectivity ensures the existence of at least one $$x\in A$$ with $$f(x)=y$$. Choose one such $$x$$ (using the axiom of choice if necessary) and define $$g(y)=x$$. Then $$f(g(y)) = y$$ for every $$y\in B$$, i.e. $$f\circ g = I_B$$. Hence a right inverse $$g$$ exists and Statement 2 is also true.
Step 3: Does Statement 2 explain Statement 1?
Statement 1 is true solely because “bijective” already includes “onto.” While Statement 2 is a separate characterisation of surjectivity, it is not used as the reason in Statement 1; the onto property follows directly from the definition of bijection, not from the existence of a right inverse highlighted in Statement 2. Therefore Statement 2 is not the correct explanation for Statement 1.
Hence the correct option is:
Option D which is: Statement 1 is true, Statement 2 is true, Statement 2 is not the correct explanation for Statement 1.
The range of the function $$f(x) = \dfrac{x}{1+|x|}, x \in R$$, is
Consider the following statements P: Suman is brilliant; Q: Suman is rich; R: Suman is honest. The negation of the statement "Suman is brilliant and dishonest if and only if Suman is rich" can be expressed as:
The domain of the function $$f(x) = \dfrac{1}{\sqrt{|x| - x}}$$ is:
The given function is $$f(x)=\dfrac{1}{\sqrt{|x|-x}}$$.
For any real-valued function that contains a square root in the denominator, both of the following conditions must hold:
1. The radicand (the quantity inside the square root) must be strictly positive: $$|x|-x \gt 0$$,
2. The denominator itself must be non-zero, which is already ensured if the radicand is positive.
Evaluate the radicand case-wise because of the absolute value:
Case 1: $$x \ge 0$$Then $$|x| = x$$, so $$|x|-x = x-x = 0$$. The inequality $$0 \gt 0$$ is impossible; hence no $$x \ge 0$$ satisfies the condition.
Case 2: $$x \lt 0$$Now $$|x| = -x$$ (since $$x$$ is negative). Therefore,
$$|x|-x = (-x)-x = -2x.$$
Because $$x \lt 0$$, we have $$-2x \gt 0$$ automatically. Thus every negative real number satisfies the required inequality.
Combining the two cases, the only allowable values are all real numbers less than zero:
$$\boxed{(-\infty,\,0)}$$.
Hence the domain matches Option B: $$(-\infty, 0)$$.
Let $$S$$ be a non-empty subset of $$R$$. Consider the following statement: P: There is a rational number $$x \in S$$ such that $$x > 0$$. Which of the following statements is the negation of the statement $$P$$?
Statement-1: $$\sim (p \leftrightarrow \sim q)$$ is equivalent to $$p \leftrightarrow q$$. Statement-2: $$\sim (p \leftrightarrow \sim q)$$ is a tautology.
For real $$x$$, let $$f(x) = x^3 + 5x + 1$$, then
Let $$f(x) = (x + 1)^2 - 1, x \geq -1$$. Statement-1: The set $$\{x : f(x) = f^{-1}(x)\} = \{0, -1\}$$ Statement-2 : f is a bijection.
Let $$p$$ be the statement "$$x$$ is an irrational number", $$q$$ be the statement "$$y$$ is a transcendental number", and $$r$$ be the statement "$$x$$ is a rational number iff $$y$$ is a transcendental number". Statement-1: $$r$$ is equivalent to either $$q$$ or $$p$$. Statement-2: $$r$$ is equivalent to $$\sim(p \leftrightarrow \sim q)$$.
The statement $$p \to (q \to p)$$ is equivalent to
Let $$f: N \to Y$$ be a function defined as $$f(x) = 4x + 3$$, where $$Y = \{y \in N : y = 4x + 3$$ for some $$x \in N\}$$. Show that f is invertible and its inverse is
The function is $$f:N \rightarrow Y$$ defined by $$f(x)=4x+3$$, where $$N=\{1,2,3,\dots\}$$ and $$Y=\{\,y \in N \mid y=4x+3 \text{ for some } x\in N\}$$.
Step 1: Verify injectivity
Assume $$f(x_1)=f(x_2)$$. Then
$$4x_1+3 = 4x_2+3$$
$$\Rightarrow 4x_1 = 4x_2$$
$$\Rightarrow x_1 = x_2$$.
Hence $$f$$ is one-one (injective).
Step 2: Verify surjectivity
Take any $$y \in Y$$. By definition of $$Y$$, there exists some $$x \in N$$ such that
$$y = 4x+3 = f(x)$$.
Thus every element of $$Y$$ is an image of some element of $$N$$, so $$f$$ is onto (surjective).
Since $$f$$ is both injective and surjective, it is bijective, therefore invertible.
Step 3: Find the inverse rule
Start with $$y=f(x)=4x+3$$.
Solve for $$x$$:
$$4x = y-3 \;\;\Rightarrow\;\; x = \frac{y-3}{4}$$.
Define $$g:Y \rightarrow N$$ by
$$g(y)=\frac{y-3}{4}$$.
Step 4: Verify that $$g$$ is the inverse
1. $$g(f(x)) = g(4x+3)=\frac{(4x+3)-3}{4}=x$$ for every $$x\in N$$.
2. $$f(g(y))=f\!\left(\frac{y-3}{4}\right)=4\!\left(\frac{y-3}{4}\right)+3 = y$$ for every $$y\in Y$$.
Both compositions give the respective identity functions, so $$g=f^{-1}$$.
Therefore the inverse of $$f$$ is $$g(y)=\frac{y-3}{4}$$.
Option D which is: $$g(y)=\dfrac{y-3}{4}$$
The largest interval lying in $$\left(-\frac{\pi}{2}, \frac{\pi}{2}\right)$$ for which the function $$\left[f(x) = 4^{-x^2} + \cos^{-1}\left(\frac{x}{2} - 1\right) + \log(\cos x)\right]$$ is defined, is
The domain of $$f(x) = 4^{-x^{2}} + \cos^{-1}\!\left(\frac{x}{2}-1\right) + \log(\cos x)$$ is the set of all real numbers that satisfy the individual domain conditions of every term appearing in the expression.
Since the question itself restricts us to $$\left(-\frac{\pi}{2},\frac{\pi}{2}\right)$$, we will enforce this outer restriction at the end. Let us examine each term one by one.
1. The exponential term $$4^{-x^{2}}$$
The base 4 is positive, so $$4^{(\text{anything})}$$ is defined for every real $$x$$. Hence this term imposes no extra restriction.
2. The inverse-cosine term $$\cos^{-1}\!\left(\frac{x}{2}-1\right)$$
For the principal value of $$\cos^{-1}(y)$$ to be defined, its argument must satisfy $$-1 \le y \le 1$$. Therefore
$$-1 \le \frac{x}{2}-1 \le 1.$$
Solving these two inequalities:
Lower bound:
$$\frac{x}{2}-1 \ge -1 \quad\Longrightarrow\quad \frac{x}{2} \ge 0 \quad\Longrightarrow\quad x \ge 0.$$
Upper bound:
$$\frac{x}{2}-1 \le 1 \quad\Longrightarrow\quad \frac{x}{2} \le 2 \quad\Longrightarrow\quad x \le 4.$$
Hence from the inverse-cosine term we obtain the interval
$$0 \le x \le 4.$$
3. The logarithmic term $$\log(\cos x)$$
The natural logarithm is defined only for positive arguments, so we need
$$\cos x \gt 0.$$
Inside the given outer interval $$\left(-\frac{\pi}{2},\frac{\pi}{2}\right)$$, the cosine function is positive for every point except the endpoints, where $$\cos\!\left(\pm\frac{\pi}{2}\right)=0$$. Therefore
$$\cos x \gt 0 \quad\Longrightarrow\quad x \in\left(-\frac{\pi}{2},\frac{\pi}{2}\right)$$
with strict inequalities at both ends.
4. Combine all the restrictions
We must honour simultaneously:
• $$0 \le x \le 4$$ (from the inverse-cosine term), and
• $$x \in\left(-\frac{\pi}{2},\frac{\pi}{2}\right)$$ with open ends (from the logarithmic term).
Intersecting these two intervals gives
$$x \in [0, \frac{\pi}{2})$$
because:
• The lower endpoint 0 is allowed (cos 0 = 1 > 0 and the arccos argument equals -1, which is permitted).
• The upper endpoint $$\frac{\pi}{2}$$ is excluded because $$\cos\!\left(\frac{\pi}{2}\right)=0$$ makes the logarithm undefined.
This is the largest interval contained in $$\left(-\frac{\pi}{2},\frac{\pi}{2}\right)$$ on which every part of the function is defined.
Hence the required interval is $$\left[0, \frac{\pi}{2}\right).$$
Option D which is: $$\left[0, \frac{\pi}{2}\right)$$
A real valued function $$f(x)$$ satisfies the functional equation $$f(x - y) = f(x)f(y) - f(a - x) f(a + y)$$ where $$a$$ is a given constant and $$f(0) = 1$$, $$f(2a - x)$$ is equal to
The functional equation is
$$f(x-y)=f(x)f(y)-f(a-x)f(a+y)\qquad (\,\star\,)$$
with the given condition $$f(0)=1$$. We have to find $$f(2a-x)$$ in terms of $$f(x)$$.
Step 1: Put $$x=a$$ in $$(\star)$$
Substituting $$x=a$$ gives
$$f(a-y)=f(a)f(y)-f(a-a)f(a+y).$$
Because $$f(0)=1$$, this becomes
$$f(a-y)=f(a)f(y)-f(a+y).$$
Re-arranging, we obtain the symmetric relation
$$f(a-y)+f(a+y)=f(a)f(y)\qquad (1).$$
Step 2: Find $$f(a)$$
Set $$y=0$$ in (1):
$$f(a-0)+f(a+0)=f(a)f(0)\;\Longrightarrow\;2f(a)=f(a)\times 1.$$
Hence $$f(a)=0.$$
Step 3: Use $$f(a)=0$$ in the symmetric relation
Putting $$f(a)=0$$ back into (1) gives
$$f(a-y)+f(a+y)=0\qquad\text{for all real }y.\qquad (2)$$
Step 4: Express $$f(2a-x)$$
Choose $$y=a-x$$ in (2). Then
$$a-y=x,\qquad a+y=2a-x.$$
Equation (2) becomes
$$f(x)+f(2a-x)=0\;\Longrightarrow\;f(2a-x)=-f(x).$$
Thus $$f(2a-x)=-f(x).$$
Option A which is: $$-f(x)$$
Let $$R = \{(1, 3), (4, 2), (2, 4), (2, 3), (3, 1)\}$$ be a relation on the set $$A = \{1, 2, 3, 4\}$$. The relation $$R$$ is
The relation R is neither reflexive, nor symmetric, nor transitive.
Given set and relation:
$$ A = \{1, 2, 3, 4\} $$
$$ R = \{(1, 3), (4, 2), (2, 4), (2, 3), (3, 1)\} $$
Reflexivity check:
A relation is reflexive if $$ (a, a) \in R $$ for all $$ a \in A $$.
$$ (1, 1) \notin R $$
Therefore, R is not reflexive.
Symmetry check:
A relation is symmetric if $$ (a, b) \in R \implies (b, a) \in R $$.
$$ (2, 3) \in R $$
$$ (3, 2) \notin R $$
Therefore, R is not symmetric.
Transitivity check:
A relation is transitive if $$ (a, b) \in R \text{ and } (b, c) \in R \implies (a, c) \in R $$.
$$ (4, 2) \in R \text{ and } (2, 3) \in R $$
$$ (4, 3) \notin R $$
Therefore, R is not transitive.
Final Answer:
The relation R is not reflexive, not symmetric, and not transitive.From options it is Not Symmetric.
If $$f: R \to S$$, defined by $$f(x) = \sin x - \sqrt{3}\cos x + 1$$, is onto, then the interval of $$S$$ is
The graph of the function $$y = f(x)$$ is symmetrical about the line $$x = 2$$, then
Let a function be symmetrical about a vertical line given by:
$$ x = a $$
Geometrically, this means that if we move a distance of x to the right of the line or a distance of x to the left of the line, the corresponding outputs of the function are identical. This property can be written as:
$$ f(a + x) = f(a - x) $$
The problem states that the graph is symmetrical about the specific line:
$$ x = 2 $$
Substitute the value of $$ a = 2 $$ into the symmetry relation formula:
$$ f(2 + x) = f(2 - x) $$
Final Answer:
The mathematical relation for the symmetry is $$ f(2 + x) = f(2 - x) $$.
The domain of the function $$f(x) = \frac{\sin^{-1}(x - 3)}{\sqrt{9 - x^2}}$$ is
Let the given function be:
$$ f(x) = \frac{\sin^{-1}(x - 3)}{\sqrt{9 - x^2}} $$
For the function to be defined, the conditions for both the numerator and the denominator must be satisfied simultaneously.
Condition 1: Domain of the inverse sine function in the numerator.
The argument of the inverse sine function must lie within the closed interval from -1 to 1:
$$ -1 \leq x - 3 \leq 1 $$
Add 3 to all parts of the inequality to isolate x:
$$ -1 + 3 \leq x \leq 1 + 3 $$
$$ 2 \leq x \leq 4 $$
This gives the first valid interval for x:
$$ x \in [2, 4] $$
Condition 2: Domain of the square root function in the denominator.
The expression inside the square root in the denominator must be strictly greater than 0 because division by 0 is undefined:
$$ 9 - x^2 > 0 $$
Rearrange the inequality by multiplying by -1, which flips the inequality sign:
$$ x^2 - 9 < 0 $$
Factor the difference of squares:
$$ (x - 3)(x + 3) < 0 $$
This quadratic inequality is satisfied when x lies strictly between the two roots:
$$ -3 < x < 3 $$
This gives the second valid interval for x:
$$ x \in (-3, 3) $$
To find the domain of the complete function, take the intersection of the two individual intervals:
$$ \text{Domain} = [2, 4] \cap (-3, 3) $$
Comparing the boundaries, the lower bound must be at least 2, and the upper bound must be strictly less than 3. Combining these restrictions yields:
$$ 2 \leq x < 3 $$
Written in interval notation, this represents a half-open interval.
Final Answer:
The domain of the function is $$ [2, 3) $$.
Frequently Asked Questions
JEE Sets, Relations and Functions questions test concepts such as set operations, relations, function properties, domain, range, and function composition. These topics are asked in both JEE Main and JEE Advanced.
Yes, this chapter forms the foundation of many Mathematics concepts used throughout the JEE syllabus. It also contributes 1–2 direct questions in the exam.
Function types such as injective, surjective, and bijective functions are highly important. Domain and range-based questions are also frequently asked in JEE.
This chapter is generally considered easy to moderate. Most questions are concept-based and require a clear understanding of definitions and properties.
JEE Main typically asks 1–2 questions from this chapter. JEE Advanced may include conceptual questions involving functions and equivalence relations.
Practice topic-wise previous year questions and focus on function types, domain, and range problems. Regular revision of definitions and properties is also important.
Students often overlook domain restrictions and confuse injective and surjective functions. Incomplete checking of relation properties is another common mistake.
An injective function maps different inputs to different outputs. A surjective function covers every element of the codomain, while a bijective function satisfies both conditions.

