Differentiation Question 373

Question: If f be a polynomial, then the second derivative of $ f(e^{x}) $ is

[Karnataka CET 1999]

Options:

A) $ {f}’(e^{x}) $

B) $ {f}’’(e^{x})e^{x}+{f}’(e^{x}) $

C) $ {f}’’(e^{x})e^{2x}+{f}’’(e^{x}) $

D) $ {f}’’(e^{x})e^{2x}+{f}’(e^{x})e^{x} $

Show Answer

Answer:

Correct Answer: D

Solution:

Let $ y=f(e^{x}) $

Therefore $ \frac{dy}{dx}={f}’(e^{x})e^{x} $

$ \frac{d^{2}y}{dx^{2}}={f}’’(e^{x}).e^{x}.e^{x}+e^{x}.{f}’(e^{x}) $ = $ f’’(e^{x}).e^{2x}+f’(e^{x}).e^{x} $ .