JEE Main & Advanced Mathematics Differentiation Question Bank Differentiation by Substitution

  • question_answer
    If f be a polynomial, then the second derivative of \[f({{e}^{x}})\] is                   [Karnataka CET 1999]

    A)            \[{f}'({{e}^{x}})\]

    B)            \[{f}''\,({{e}^{x}})\,{{e}^{x}}+{f}'({{e}^{x}})\]

    C)            \[{f}''\,({{e}^{x}}){{e}^{2x}}+{f}''({{e}^{x}})\]

    D)            \[{f}''\,({{e}^{x}}){{e}^{2x}}+{f}'\,({{e}^{x}})\,{{e}^{x}}\]

    Correct Answer: D

    Solution :

               Let \[y=f({{e}^{x}})\] Þ \[\frac{dy}{dx}={f}'({{e}^{x}})\,{{e}^{x}}\]            \[\frac{{{d}^{2}}y}{d{{x}^{2}}}={f}''({{e}^{x}}).{{e}^{x}}.{{e}^{x}}+{{e}^{x}}.{f}'({{e}^{x}})\]=\[f''({{e}^{x}}).{{e}^{2x}}+f'({{e}^{x}}).{{e}^{x}}\].


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