Question
Let $f$ be defined on $[-5,5]$ as $f(x)=\left\{\begin{array}{l} x \text { if } x \text { is rational } \\ -x \text { if } x \text { is irrational }\end{array}\right.$ Then $f(x)$ is

Answer

As $x \rightarrow 0$ both $x$ and $-x$ tend to zero, $f(0)=0$
$\therefore f(x)$ is continuous at $x=0$.
For $x \neq 0, x \neq-x, f(x)$ is discontinuous.

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