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Question: Answered & Verified by Expert
A value of $C$ for which the conclusion of Mean Value Theorem holds for the function $f(x)=$ $\log _{\mathrm{e}} x$ on the interval $[1,3]$ is
MathematicsApplication of DerivativesJEE MainJEE Main 2007
Options:
  • A
    $2 \log _3 e$
  • B
    $\frac{1}{2} \log _{\mathrm{e}} 3$
  • C
    $\log _3 e$
  • D
    $\log _e 3$
Solution:
1074 Upvotes Verified Answer
The correct answer is:
$2 \log _3 e$
Using mean value theorem
$\begin{aligned}
& f^{\prime}(c)=\frac{f(3)-f(1)}{3-1} \\
& \Rightarrow \frac{1}{c}=\frac{\log 3-\log 1}{2} \\
& \Rightarrow c=\frac{2}{\log _e 3}=2 \log _3 e.
\end{aligned}$

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