Sign in
Please select an account to continue using cracku.in
↓ →
Let f and g be two functions defined by $$f(x) = \mid x + \mid x \mid \mid$$ and $$g(x) = \frac{1}{x}$$ for $$x \neq 0$$. If $$f(a) + g(f(a)) = \frac{13}{6}$$ for some real a, then the maximum possible value of $$f(g(a))$$ is:
Correct Answer: 6
Given that f(a) + g(f(a)) = $$\dfrac{\ 13}{6}$$
f(a) + $$\dfrac{\ 1}{f\left(a\right)}$$ = $$\dfrac{\ 13}{6}$$
$$6(f(a))^2-13\left(f\left(a\right)\right)+6\ =\ 0$$
f(a) = $$\dfrac{13\pm\sqrt{13^2-24\left(6\right)\ }\ }{2\times6}$$
this implies , f(a) = $$\ \dfrac{\ 3}{2}\ (or)\ \dfrac{\ 2}{3}$$
Given that f(a) = |a+|a||
if $$a\le0\ $$, f(a) = |a-a| = 0
else if $$a\ge\ 0$$ , then f(a) = 2a.
Therefore , 2a = $$\ \dfrac{\ 3}{2}\ (or)\ \dfrac{\ 2}{3}$$
that is, a = $$\ \dfrac{\ 3}{4}\ (or)\ \dfrac{\ 1}{3}$$
g($$\dfrac{\ 3}{4}$$) = $$\dfrac{\ 4}{3}$$
g($$\dfrac{\ 1}{3}$$) = $$\dfrac{\ 3}{1}$$
Therefore f(g(a)) = $$\dfrac{\ 8}{3}$$ or 6.
Maximum value is 6.
Create a FREE account and get: