Q. Let $f:R \rightarrow R$ be a differentiable function having$f(2) = 6,\ f^{'}(2) = \left( \frac{1}{48} \right)$. Then, $\lim_{x \rightarrow 2}\frac{\int_{6}^{f(x)}{4\ t^{3}\ dt}}{x - 2}$ is equals

A) 18
B) 12
C) 36
D) 24
Explanation

(a)
$\lim_{x \rightarrow 2}\frac{\int_{6}^{f(x)}{4\ t^{3}\ dt}}{x - 2}\lim_{x \rightarrow 2}{\frac{4\left\{ f(x) \right\}^{3}}{1}.f^{'}(x)}$
$= 4\left\{ f(2) \right\}^{3}.f^{'}(2)$
$= 4 \times (6)^{3}.\frac{1}{48}$
$= 18$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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