MCQ
If $f(x)=\left\{\begin{array}{l}x \text { for } x \leq 0 \\ 0 \text { for } x > 0\end{array}\right.$ then $f(x)$ at $x=0$ is
  • Continuouss but not differentiable
  • B
    Not continuous but differentiable
  • C
    Continuous and differentiable
  • D
    Not continuous and not differentiable

Answer

Correct option: A.
Continuouss but not differentiable
$\because \lim _{x \rightarrow 0^{-}} f(x)=\lim _{x \rightarrow 0} x=0$
and $\lim _{x \rightarrow 0^{+}} f(x)=0, f(0)=0$
$\therefore  f(x)$ is continuous at $x=0$.
For differentiability, $f^{\prime}(x)=\left\{\begin{array}{ll}1 & x \leq 0 \\ 0 & x>0\end{array}\right.$
$\therefore f(x)$ is not differentiable.

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