CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    \[\int_{0}^{1}{x{{e}^{-5x}}dx}\]is equal to

    A)  \[\frac{1}{25}-\frac{6{{e}^{-5}}}{25}\]                   

    B)  \[\frac{1}{25}+\frac{6{{e}^{-5}}}{25}\]

    C)  \[-\frac{1}{25}-\frac{6{{e}^{-5}}}{25}\] 

    D)         \[\frac{1}{25}-\frac{1}{5}{{e}^{-5}}\]

    E)  \[\frac{1}{25}+\frac{1}{5}{{e}^{-5}}\]

    Correct Answer: A

    Solution :

    \[\int_{0}^{1}{\underset{I}{\mathop{x}}\,}\,\,\underset{II}{\mathop{{{e}^{-5x}}}}\,dx\] \[=\left[ \left\{ x\left( \frac{{{e}^{-5x}}}{-5} \right) \right\} \right]_{0}^{1}-\left\{ \int_{0}^{1}{1.\frac{{{e}^{-5x}}}{-5}dx} \right\}\] \[=\left[ -\frac{x{{e}^{-5x}}}{5}-\frac{{{e}^{-5x}}}{25} \right]_{0}^{1}\] \[=-\frac{{{e}^{-5}}}{5}-\frac{{{e}^{-5}}}{25}+\frac{1}{25}\] \[=-\frac{6{{e}^{-5}}}{25}+\frac{1}{25}=\frac{1}{25}-\frac{6{{e}^{-5}}}{25}\]        


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