JEE Main & Advanced Mathematics Functions Question Bank Self Evaluation Test - Relation and Functions-II

  • question_answer
    The inverse of \[f(x)=\frac{2}{3}\frac{{{10}^{x}}-{{10}^{-x}}}{{{10}^{x}}+{{10}^{-x}}}\] is

    A) \[\frac{1}{3}{{\log }_{10}}\frac{1+x}{1-x}\]     

    B) \[\frac{1}{2}{{\log }_{10}}\frac{2+3x}{2-3x}\]

    C) \[\frac{1}{3}{{\log }_{10}}\frac{2+3x}{2-3x}\]

    D) \[\frac{1}{6}{{\log }_{10}}\frac{2-3x}{2+3x}\]

    Correct Answer: B

    Solution :

    [b] if \[y=\frac{2}{3}\frac{{{10}^{x}}-{{10}^{-x}}}{{{10}^{x}}+{{10}^{-x}}},{{10}^{2x}}=\frac{3y+2}{2-3y}\] or \[x=\frac{1}{2}{{\log }_{10}}\frac{2+3y}{2-3y}\] \[\therefore {{f}^{-1}}(x)=\frac{1}{2}{{\log }_{10}}\frac{2+3x}{2-3x}.\]


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