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

  • question_answer
    If f(x) is an invertible function and \[g(x)=2f(x)+5,\] then the value of \[{{g}^{-1}}(x)\] is

    A) \[2{{f}^{-1}}(x)-5\]

    B) \[\frac{1}{2{{f}^{-1}}(x)+5}\]

    C) \[\frac{1}{2}{{f}^{-1}}(x)+5\]

    D) \[{{f}^{-1}}\left( \frac{x-5}{2} \right)\]

    Correct Answer: D

    Solution :

    [d] Replacing x by \[{{g}^{-1}}(x),\] we get \[x=2f({{g}^{-1}}(x))+5\] \[\therefore f({{g}^{-1}}(x))=\frac{x-5}{2}\] \[\therefore {{g}^{-1}}(x)={{f}^{-1}}\left( \frac{x-5}{2} \right)\]


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