Let $f(x)=\left[x^{2}-x\right]+|-x+[x]|$, where $x \in \mathbb{R}$ and $[t]$ denotes the greatest integer less than or equal to $t$. Then, $f$ is :
Solution
We have,
<br/><br/>$$\begin{aligned}
f(x) & =\left[x^2-x\right]+|-x+[x]| \\\\
& =[x(x-1)]+\{x\}
\end{aligned}
$$
<br/><br/>$$
f(x)=\left\{\begin{array}{ccc}
x+1 & ; & -0.5 < x < 0 \\
0 & ; & x=0 \\
-1+x & ; & 0 < x <1 \\
0 & ; & x=1 \\
x-1 & ; & 1 < x < 1.5
\end{array}\right.
$$
<br/><br/>At $x=0$,
<br/><br/>$$
\begin{array}{r}
\text { LHL }=\lim\limits_{x \rightarrow 0^{-}} f(x)=1 \\\\
\text { RHL } \lim\limits_{x \rightarrow 0^{+}} f(x)=-1 \\\\
f(0)=0
\end{array}
$$
<br/><br/>$\therefore f(x)$ is not continuous at $x=0$
<br/><br/>At $x=1$
<br/><br/>$$
\begin{aligned}
\mathrm{LHL} & =\lim _{x \rightarrow 1^{-}} f(x)=-1+1=0 \\\\
\mathrm{RHL} & =\lim _{x \rightarrow 1^{+}} f(x)=1-1=0 \\\\
f(1) & =0
\end{aligned}
$$
<br/><br/>$\therefore f(x)$ is continuous at $x=1$
<br/><br/>Hence, $f(x)$ is continuous at $x=1$, but not continuous at $x=0$.
About this question
Subject: Mathematics · Chapter: Limits, Continuity and Differentiability · Topic: Limits and Standard Results
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