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

  • question_answer
    If \[f(x)=5lo{{g}_{5}}x\] then \[{{f}^{-1}}(\alpha -\beta )\] where \[\alpha ,\beta \in R\]is equal to

    A) \[{{f}^{-1}}(\alpha )-{{f}^{-1}}(\beta )\]

    B) \[\frac{{{f}^{-1}}(\alpha )}{{{f}^{-1}}(\beta )}\]

    C) \[\frac{1}{f(\alpha -\beta )}\]

    D) \[\frac{1}{f(\alpha )-f(\beta )}\]

    Correct Answer: B

    Solution :

    [b] \[f(x)=5lo{{g}_{5}}x\Rightarrow {{f}^{-1}}(x)={{5}^{x/5}}\] \[{{f}^{-1}}(\alpha -\beta )={{5}^{\frac{\alpha -\beta }{5}}}=\frac{{{5}^{\alpha /5}}}{{{5}^{\beta /5}}}=\frac{{{f}^{-1}}(\alpha )}{{{f}^{-1}}(\beta )}\]


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