12th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-6

  • question_answer
    The maximum value of \[{{x}^{1/x}},x>0\]is:

    A)   \[{{\left( \frac{1}{e} \right)}^{e}}\]                 

    B)  \[{{e}^{\frac{1}{e}}}\]           

    C)  1                                

    D)  0

    Correct Answer: B

    Solution :

    [b] \[\because Let\,y={{x}^{1/x}}\] \[logy=\frac{1}{x}logx\] Differentiating both sides, we have \[\frac{1}{y}.\frac{dy}{dx}=\frac{1}{x}.\frac{1}{x}+\left( \frac{-1}{{{x}^{2}}} \right)\log x=\frac{1}{2}(1-\log x)\] For maximum and minimum value, \[\frac{dy}{dx}=0\Rightarrow {{x}^{\frac{1}{x}-2}}.(1-\log x)=0\] If \[logx=1\] \[\Rightarrow x={{e}^{1}}=e\] \[\therefore \] Maximum value of \[y={{x}^{1/x}}={{e}^{1/e}}.\] Hence, option [b] is correct.


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