Q. Let $f:R \rightarrow R$ be a differentiable function such that $f(3) = 3,\ f^{'}(3) = \frac{1}{2}$, Then, the value of $\lim_{x \rightarrow 3}\frac{\int_{3}^{f(x)}{2t^{3}dt}}{x - 3}$ is

A) 25
B) 26
C) 27
D) None of these
Explanation

(c)
$\lim_{x \rightarrow 3}\frac{\int_{3}^{f(x)}{2t^{3}dt}}{x - 3} = \lim_{x \rightarrow 3}\frac{2\left\lbrack f(x) \right\rbrack^{3}.f^{'}(x)}{1}$
$= 2\left\lbrack f(3) \right\rbrack^{3}.f^{'}(3) = {2 \times 3}^{3} \times \frac{1}{2}\$
$= 27$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.