CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2008

  • question_answer
    If \[f(x)=b{{e}^{ax}}+a{{e}^{bx}},\] then \[f'(0)\] is equal to

    A)  \[0\]                                    

    B)  \[2ab\]

    C)  \[ab(a+b)\]                       

    D)  \[ab\]

    Correct Answer: C

    Solution :

    Given,     \[f(x)=b{{e}^{ax}}+a{{e}^{bx}}\] On differentiating w.r.t. x, we get                 \[f'(x)=ab\,{{e}^{ax}}+ab\,{{e}^{bx}}\] Again, differentiating, we get                 \[f''(x)={{a}^{2}}b{{e}^{ax}}+a{{b}^{2}}\,{{e}^{bx}}\] \[\Rightarrow \]               \[f''(0)={{a}^{2}}b+a{{b}^{2}}\]                                 \[=ab(a+b)\]


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