JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation by Substitution

  • question_answer
    If \[x=\log p\]and \[y=\frac{1}{p}\], then

    A)            \[\frac{{{d}^{2}}y}{d{{x}^{2}}}-2p=0\]

    B)            \[\frac{{{d}^{2}}y}{d{{x}^{2}}}+y=0\]

    C)            \[\frac{{{d}^{2}}y}{d{{x}^{2}}}+\frac{dy}{dx}=0\]

    D)            \[\frac{{{d}^{2}}y}{d{{x}^{2}}}-\frac{dy}{dx}=0\]

    Correct Answer: C

    Solution :

               \[x=\log p\Rightarrow p={{e}^{x}}\Rightarrow y={{e}^{-x}}\]                    \[\Rightarrow \frac{dy}{dx}=-{{e}^{-x}}\] and\[\frac{{{d}^{2}}y}{d{{x}^{2}}}={{e}^{-x}};\,\,\,\therefore \frac{{{d}^{2}}y}{d{{x}^{2}}}+\frac{dy}{dx}=0\].


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