Q. The value of $f$ at $x = 0$ so that function $f(x) = \frac{2^{x} - 2^{- x}}{x},\ x \neq 0$ is continuous at $x = 0$, is

A) 0
B) $\log 2$
C) 4
D) $\log 4$
Explanation

(d)
$\lim_{x \rightarrow 0}\frac{2^{x} - 2^{- x}}{x} = \lim_{x \rightarrow 0}\ 2^{x}\log{2 + 2^{- x}\log 2}$
[by L’ Hospital’s rule]
$= \log 4$
Since, the function is continuous at $x = 0$
$\therefore\ \ \ \ \ \ f(0) = \lim_{x \rightarrow 0}\ f(x)\ \ \Rightarrow \ \ \ \ f(0) = \log 4$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

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