Show that $f(x)=x^{1 / 3}$ is not differentiable at $x=0$.
Disclaimer: It might be a wrong question because $f(x)$ is differentiable at $x=0$
Given: $f(x)=x^{\frac{1}{3}}$
We have,
$(\mathrm{LHD}$ at $x=0)$
$\lim _{x \rightarrow 0^{-}} \frac{f(x)-f(0)}{x-0}$
$=\lim _{h \rightarrow 0} \frac{f(0-h)-f(0)}{0-h-0}$
$=\lim _{h \rightarrow 0} \frac{(0-h)^{\frac{1}{3}}-0^{\frac{1}{3}}}{-h}$
$=\lim _{h \rightarrow 0} \frac{(-h)^{\frac{1}{3}}}{-h}$
$=\lim _{h \rightarrow 0}(-h)^{\frac{-2}{3}}$
$=0$
(RHD at x = 0)
$\lim _{x \rightarrow 0^{+}} \frac{f(x)-f(0)}{x-0}$
$=\lim _{h \rightarrow 0} \frac{f(0+h)-f(0)}{0+h-0}$
$=\lim _{h \rightarrow 0} \frac{(0+h)^{\frac{1}{3}}-0^{\frac{1}{3}}}{-h}$
$=\lim _{h \rightarrow 0} \frac{h^{\frac{1}{3}}}{h}$
$=\lim _{h \rightarrow 0} h^{\frac{-2}{3}}$
$=0$
LHD at (x = 0)= RHD at (x = 0)
Hence, $f(x)=x^{\frac{1}{3}}$ is differentiable at $x=0$