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The roots of the quadratic equation $$3x^{2} - px + q = 0$$ are $$10^{th}$$ and $$11^{th}$$ terms of an arithmetic progression with common difference $$\frac{3}{2}$$. If the sum of the first 11 terms of this arithmetic progression is 88 , then q - 2p is equal to
Correct Answer: 474
Let the roots of $$3x^{2} - px + q = 0$$ be $$\alpha$$ and $$\beta$$.
It is given that $$\alpha$$ and $$\beta$$ are the 10th and 11th term of an A.P with a common difference of $$\dfrac{3}{2}$$.
10th term = $$a+9d$$ = $$a+\left(9\times\dfrac{3}{2}\right)$$ = $$a+\dfrac{27}{2}$$
11th term = $$a+10d$$ = $$a+\left(10\times\dfrac{3}{2}\right)$$ = $$a+15$$
Now, it is given that the sum of the first 11 terms of the A.P is 88.
$$\dfrac{11}{2}\times\left(a+\left(a+15\right)\right)=88$$
$$2a+15=16$$
$$a=\ \dfrac{1}{2}$$
10th term = $$\dfrac{1}{2}+\dfrac{27}{2}=14$$
11th term = $$\dfrac{1}{2}+15=\dfrac{31}{2}$$
So, $$\alpha=14$$ and $$\beta=\dfrac{31}{2}$$
Now, in $$3x^{2} - px + q = 0$$,
$$\alpha+\beta=\dfrac{p}{3}$$
$$14+\dfrac{31}{2}=\dfrac{p}{3}$$
$$\dfrac{28+31}{2}=\dfrac{p}{3}$$
$$p=\dfrac{59\times3}{2}$$
$$\alpha\times\beta=\dfrac{q}{3}$$
$$14\times\dfrac{31}{2}=\dfrac{q}{3}$$
$$q=7\times31\times3$$
$$q=651$$
Now, $$q-2p$$ = $$651-\left(2\times\dfrac{59\times3}{2}\right)$$
$$q-2p$$ = $$651-177=474$$
Hence, the value of $$(q-2p)$$ is 474.
$$\therefore\ $$ The required answer is 474.
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