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Question: Answered & Verified by Expert
Let $f: D \rightarrow R$ where $D=[0,1] \cup[2,4]$ be defined by $f(x)=\left\{\begin{array}{ll}x, & \text { if } x \in[0,1] \\ 4-x, & \text { if } x \in[2,4]\end{array}\right.$. Then,
MathematicsApplication of DerivativesWBJEEWBJEE 2021
Options:
  • A Rolle's theorem is applicable to $\mathrm{f}$ in $\mathrm{D}$
  • B Rolle's theorem is not applicable to $\mathrm{f}$ in $\mathrm{D}$
  • C there exists $\xi \in \mathrm{D}$ for which $\mathrm{f}^{\prime}(\xi)=0$ but Rolle's theorem is not applicable
  • D $f$ is not continuous in $D$
Solution:
2807 Upvotes Verified Answer
The correct answer is: Rolle's theorem is not applicable to $\mathrm{f}$ in $\mathrm{D}$


$f(x)=\left\{\begin{array}{ll}x, & x \in[0,1] \\ 4-x, & x \in[2,4]\end{array}\right.$
$f(x)$ is increasing in $[0,1]$
and $f(x)$ is decreasing in $[2,4]$
$\therefore$ Rolle's theorem is not applicable to $\mathrm{f}$ in $\mathrm{D}$.

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