JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation by Substitution

  • question_answer
    If \[y={{e}^{{{\tan }^{-1}}x}}\], then \[(1+{{x}^{2}})\frac{{{d}^{2}}y}{d{{x}^{2}}}=\]

    A)            \[(1-2x)\frac{dy}{dx}\]

    B)            \[-2x\frac{dy}{dx}\]

    C)            \[-x\frac{dy}{dx}\]

    D)            0

    Correct Answer: A

    Solution :

               \[y={{e}^{{{\tan }^{-1}}x}}\Rightarrow \frac{dy}{dx}=\frac{{{e}^{{{\tan }^{-1}}x}}}{1+{{x}^{2}}}\]                    \[\Rightarrow \frac{{{d}^{2}}y}{d{{x}^{2}}}=\frac{(1+{{x}^{2}}).\frac{{{e}^{{{\tan }^{-1}}x}}}{(1+{{x}^{2}})}-{{e}^{{{\tan }^{-1}}x}}(2x)}{{{(1+{{x}^{2}})}^{2}}}\]                    \[\Rightarrow \frac{{{d}^{2}}y}{d{{x}^{2}}}=\frac{(1-2x){{e}^{{{\tan }^{-1}}x}}}{{{(1+{{x}^{2}})}^{2}}}\]\[\Rightarrow \frac{{{d}^{2}}y}{d{{x}^{2}}}(1+{{x}^{2}})=(1-2x)\frac{dy}{dx}\].


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