JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration of Rational Function by Using Partial Fractions

  • question_answer
    \[\int_{{}}^{{}}{\frac{dx}{x({{x}^{5}}+1)}}=\]          [UPSEAT 2004]

    A)                 \[\frac{1}{5}\log {{x}^{5}}({{x}^{5}}+1)+c\]

    B)                 \[\frac{1}{5}\log {{x}^{5}}\left( \frac{1+{{x}^{5}}}{{{x}^{5}}} \right)+c\]             

    C)                 \[\frac{1}{5}\log {{x}^{5}}\left( \frac{{{x}^{5}}}{{{x}^{5}}+1} \right)+c\]

    D)                 None of these

    Correct Answer: D

    Solution :

                       We have \[I=\int{\frac{dx}{x({{x}^{5}}+1)}}=\int{\frac{dx}{{{x}^{6}}\left( 1+\frac{1}{{{x}^{5}}} \right)}}\]                    Put \[1+\frac{1}{{{x}^{5}}}=t\] Þ \[\frac{-5}{{{x}^{6}}}dx=dt\]                     Þ \[I=-\frac{1}{5}\int{\frac{dt}{t}=-\frac{1}{5}}\log t+c\]                    \[I=-\frac{1}{5}\log \left( 1+\frac{1}{{{x}^{5}}} \right)+c=-\frac{1}{5}\log \left( \frac{{{x}^{5}}+1}{{{x}^{5}}} \right)+c\]                 \ \[I=\frac{1}{5}\log \left( \frac{{{x}^{5}}}{{{x}^{5}}+1} \right)+c\].


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