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If F ( X ) = Log ( 1 + X 1 − X ) , Then F ( 2 X 1 + X 2 ) is Equal To(A) {F(X)}2 (B) {F(X)}3 (C) 2f(X) (D) 3f(X) - Mathematics

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Question

If \[f\left( x \right) = \log \left( \frac{1 + x}{1 - x} \right)\] , then \[f\left( \frac{2x}{1 + x^2} \right)\]  is equal to

 

 

Options

  • (a) {f(x)}2

  • (b) {f(x)}3

  • (c) 2f(x)

  • (d) 3f(x)

     
MCQ

Solution

(c) 2f(x

\[f\left( x \right) = \log \left( \frac{1 + x}{1 - x} \right)\]
\[\text{ Then } , f\left( \frac{2x}{1 + x^2} \right) = \log \left( \frac{1 + \frac{2x}{1 + x^2}}{1 - \frac{2x}{1 + x^2}} \right)\]
\[ = \log \left( \frac{\frac{1 + x^2 + 2x}{1 + x^2}}{\frac{1 + x^2 - 2x}{1 + x^2}} \right)\]
\[ = \log \left( \frac{(1 + x )^2}{(1 - x )^2} \right)\]
\[ = 2 \log \left( \frac{1 + x}{1 - x} \right)\]
\[ = 2 (f(x))\]

 

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Chapter 3: Functions - Exercise 3.6 [Page 43]

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RD Sharma Mathematics [English] Class 11
Chapter 3 Functions
Exercise 3.6 | Q 11 | Page 43

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