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The Function F ( X ) = { E 1 / X − 1 E 1 / X + 1 , X ≠ 0 0 , X = 0 (A) is Continuous at X = 0 (B) is Not Continuous at X = 0 (C) is Not Continuous at X = 0, but Can Be Made Continuous at X = 0 - Mathematics

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Question

The function  \[f\left( x \right) = \begin{cases}\frac{e^{1/x} - 1}{e^{1/x} + 1}, & x \neq 0 \\ 0 , & x = 0\end{cases}\]

 

Options

  • is continuous at x = 0

  • is not continuous at x = 0

  • is not continuous at x = 0, but can be made continuous at x = 0

  • none of these

MCQ
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Solution

is not continuous at x = 0

Given:  

\[f\left( x \right) = \begin{cases}\frac{e^{1/x} - 1}{e^{1/x} + 1}, & x \neq 0 \\ 0 , & x = 0\end{cases}\]

We have

\[\lim_{x \to 0} f\left( x \right) = \lim_{x \to 0} \left( \frac{e^\frac{1}{x} - 1}{e^\frac{1}{x} + 1} \right)\]

If \[e^\frac{1}{x} = t\] , then

 \[x \to 0, t \to \infty\]

Also,

\[f\left( 0 \right) = 0\]

\[\therefore \lim_{x \to 0} f\left( x \right) \neq f\left( 0 \right)\]

Hence,

\[f\left( x \right)\] is discontinuous at  \[x = 0\] .
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Chapter 9: Continuity - Exercise 9.4 [Page 43]

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RD Sharma Mathematics [English] Class 12
Chapter 9 Continuity
Exercise 9.4 | Q 9 | Page 43

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