Q. If $f:( - 1,1) \rightarrow R$ be a differentiable function with $f(0) = - 1$ and $f^{'}(0) = 1.$ Let g($x) = \left\lbrack f\left( 2f(x) + 2 \right) \right\rbrack^{2}$. Then, $g^{'}(0)$ is equal to

A) 4
B) $- 4$
C) 0
D) $- 2$
Explanation

(b)
G$iven\ ,g(x) = \lbrack f{\left( 2f(x) + 2 \right)\rbrack}^{2}$
$\therefore g^{'}(x) = 2.f\left( 2f(x) + 2 \right).f^{'}\left( 2f(x) + 2 \right).2f^{'}(x)$
$= 4\ f\left( 2f(x) + 2 \right)f^{'}\left( 2f(x) + 2 \right)f^{'}(x)$
$\therefore g^{'}(0) = 4f(0)f^{'}(0)f^{'}(0) = - 4$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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