BCECE Engineering BCECE Engineering Solved Paper-2011

  • question_answer
    If \[{{I}_{m,n}}=\int_{0}^{1}{{{x}^{m}}{{(\log x)}^{n}}}dx,\]then it  is equal to

    A)  \[\frac{n}{n+1}{{I}_{m,n}}_{-1}\]                      

    B)         \[\frac{-m}{n+1}{{I}_{m,n-1}}\]                         

    C)         \[\frac{-n}{m+1}{{I}_{m,n-1}}\]                         

    D)         None of the above

    Correct Answer: C

    Solution :

    \[{{I}_{m,n}}=\int_{0}^{1}{{{x}^{m}}{{(\log x)}^{n}}dx}\] \[=\left[ {{(\log x)}^{n}}.\frac{{{x}^{m+1}}}{m+1} \right]_{0}^{1}\] \[-\int_{0}^{1}{n{{(\log x)}^{n-1}}.\frac{1}{x}.\frac{{{x}^{m+1}}}{(m+1)}dx}\] \[=0-\frac{n}{(m+1)}\int_{0}^{1}{{{x}^{m}}{{(\log x)}^{n-1}}dx}\] \[=\frac{-n}{m+1}.{{I}_{m,n-1}}\]


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