JCECE Engineering JCECE Engineering Solved Paper-2014

  • question_answer
    \[f(x)=\sqrt{ax}+\frac{{{a}^{2}}}{\sqrt{ax}}\], then\[f'(\alpha )\] is equal to

    A) \[-1\]                                    

    B) \[1\]

    C) \[0\]                                     

    D) \[a\]

    Correct Answer: C

    Solution :

    Given,\[f(x)=\sqrt{ax}+\frac{{{a}^{2}}}{\sqrt{ax}}\], Then,\[f'(x)=\frac{\sqrt{a}}{2\sqrt{x}}+\frac{{{a}^{2}}}{\sqrt{a}}\left( -\frac{1}{2}{{x}^{-3/2}} \right)\] \[\Rightarrow \]               \[f'(x)=\frac{\sqrt{a}}{2\sqrt{x}}-\frac{{{a}^{2}}}{2\sqrt{a}}{{x}^{-3/2}}\] \[\therefore \]  \[f'(a)=\frac{\sqrt{a}}{2\sqrt{a}}-\frac{{{a}^{2}}}{2\sqrt{a}{{a}^{3/2}}}\] \[\Rightarrow \]               \[f'(a)=\frac{1}{2}-\frac{{{a}^{2}}}{2{{a}^{2}}}=0\]


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