Let $f(x) \begin{cases}=|x|+3, & \text { if } x \leq-3 \\ =-2 x, & \text { if }-3 < x < 3, \text { then } \\…

Let $f(x) \begin{cases}=|x|+3, & \text { if } x \leq-3 \\ =-2 x, & \text { if }-3 < x < 3, \text { then } \\ =6 x+2, & \text { if } x \geq 3\end{cases}$
  1. $f(x)$ is discontinuous at both $x=-3$ as well as $x=3$
  2. $f(x)$ is continuous at $x=-3$ but discontinuous at $x=3$
  3. $f(x)$ is continuous at $x=-3$ as well as $x=3$
  4. $f(x)$ of discontinuous at $x-3$ but $f(x)$ is continuous at $x=3$

Solution

We have $f(x)=-x+3$, if $x \leq-3$ $\begin{aligned} & =-2 x \text {, if }-3 < x < 3 \\ & =6 \mathrm{x}+2 \text {, if } \mathrm{x} \geq 3 \\ & \underset{x \rightarrow 3^{-}}{f(x)}=-(-3)+3=6 \text { and } \underset{x \rightarrow 3^{+}}{f(x)}=-2(-3)=6 \text { and } f(-3) \\ & =-(-3)+3=6 \\ & \end{aligned}$ Thus $\mathrm{f}(\mathrm{x})$ is continuous at $\mathrm{x}=-3$ $\underset{x \rightarrow 3^{-}}{f(x)}=-2(3)=-6 \quad \text { and } \underset{x \rightarrow 3^{+}}{f(x)}=6(3)+2=20$ Thus $\mathrm{f}(\mathrm{x})$ is not continuous at $\mathrm{x}=3$.

Asked in: MHT CET 2021 (22 Sep Shift 1)

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