KVPY Sample Paper KVPY Stream-SX Model Paper-20

  • question_answer
    The integral \[\int\limits_{1}^{e}{\left\{ {{\left( \frac{x}{e} \right)}^{2x}}-{{\left( \frac{e}{x} \right)}^{x}} \right\}}{{\log }_{e}}\] is equal to:

    A) \[\frac{1}{2}-e-\frac{1}{{{e}_{2}}}\]

    B) \[-\frac{1}{2}+\frac{1}{e}-\frac{1}{2{{e}^{2}}}\]

    C) \[\frac{3}{2}-\frac{1}{6}-\frac{1}{2{{e}^{2}}}\]

    D) \[\frac{3}{2}-e-\frac{1}{2{{e}^{2}}}\]

    Correct Answer: D

    Solution :

    \[\int\limits_{1}^{e}{{{\left( \frac{x}{e} \right)}^{2x}}{{\log }_{e}}x.dx-\int\limits_{1}^{e}{\left( \frac{e}{x} \right){{\log }_{e}}x.dx}}\]
    Let,       \[{{\left( \frac{x}{e} \right)}^{2x}}=t,{{\left( \frac{e}{x} \right)}^{x}}=v\]
    \[=\frac{1}{2}\int\limits_{\left( \frac{1}{e} \right)}^{1}{dt}+\int\limits_{e}^{1}{dv}\]\[=\frac{1}{2}\left( 1-\frac{1}{{{e}^{2}}} \right)+(1-e)=\frac{3}{2}-\frac{1}{2{{e}^{2}}}-e.\]


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