Practicing Success
Rolle's theorem is not applicable to the function $f(x)=|x|$ for $-2 \leq x \leq 2$ because |
$f$ is continuous on $[-2,2]$ $f$ is not differentiable at $x=0$ $f(-2)=f(x)$ $f$ is not a constant function |
$f$ is not differentiable at $x=0$ |
We have, $f(x)=|x|= \begin{cases}x, & x \geq 0 \\ -x, & x<0\end{cases}$ ∴ (LHD at x = 0) = $\lim\limits_{x \rightarrow 0^{-}} \frac{f(x)-f(0)}{x-0}=\lim\limits_{x \rightarrow 0^{-}} \frac{-x-0}{x-0}=-1$ and, (RHD at x = 0) = $\lim\limits_{x \rightarrow 0^{+}} \frac{f(x)-f(0)}{x-0}=\lim\limits_{x \rightarrow 0^{+}} \frac{x-0}{x-0}=1$ ∴ (LHD at x = 0) ≠ (RHD at x = 0) So, f(x) is not differentiable at x = 0. Consequently, Rolle's is not applicable to the given function. |