KVPY Sample Paper KVPY Stream-SX Model Paper-23

  • question_answer
    If g is the inverse of a function f and \[f'(x)=\frac{1}{1+{{x}^{5}}},\] then g'(x) is equal to

    A) \[1+{{x}^{5}}\]

    B) \[5{{x}^{4}}\]

    C) \[\frac{1}{1+{{(g(x))}^{5}}}\]

    D) \[1+{{(g(x))}^{5}}\]

    Correct Answer: D

    Solution :

    We have,\[f'(x)=\frac{1}{1+{{x}^{5}}}\]
    \[g(x)\] is universe of \[f(x)\].
    \[\therefore \,\,\,\,\,\,\,\,\,f(g(x))=x\]
    On differentiating, we get
    \[f'(g(x).g'(x))=1\]\[\Rightarrow \,\,\,g'\left( x \right)=\frac{1}{f'(gx)}\]\[\Rightarrow \,\,\,g'\left( x \right)=\frac{1}{\frac{1}{1+(g{{(x)}^{5}})}}\]\[\Rightarrow \,\,\,g'\left( x \right)=1+(g{{(x)}^{5}})\]


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