JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Self Evaluation Test - Integrals

  • question_answer
    \[\int\limits_{0}^{1}{\frac{1}{\left( {{x}^{2}}+16 \right)\left( {{x}^{2}}+25 \right)}dx=}\]

    A) \[\frac{1}{5}\left[ \frac{1}{4}{{\tan }^{-1}}\left( \frac{1}{4} \right)-\frac{1}{5}{{\tan }^{-1}}\left( \frac{1}{5} \right) \right]\]

    B) \[\frac{1}{9}\left[ \frac{1}{4}{{\tan }^{-1}}\left( \frac{1}{4} \right)-\frac{1}{5}{{\tan }^{-1}}\left( \frac{1}{5} \right) \right]\]

    C) \[\frac{1}{4}\left[ \frac{1}{4}{{\tan }^{-1}}\left( \frac{1}{4} \right)-\frac{1}{5}{{\tan }^{-1}}\left( \frac{1}{5} \right) \right]\]

    D) \[\frac{1}{9}\left[ \frac{1}{5}{{\tan }^{-1}}\left( \frac{1}{4} \right)-\frac{1}{5}{{\tan }^{-1}}\left( \frac{1}{5} \right) \right]\]

    Correct Answer: B

    Solution :

    [b] Let \[I=\int\limits_{0}^{1}{\frac{dx}{({{x}^{2}}+16)({{x}^{2}}+25)}}\] \[=\frac{1}{9}\int\limits_{0}^{1}{\left( \frac{1}{{{x}^{2}}+16}-\frac{1}{{{x}^{2}}+25} \right)dx}\] \[=\frac{1}{9}\left( \frac{1}{4}{{\tan }^{-1}}\frac{x}{4}-\frac{1}{5}{{\tan }^{-1}}\frac{x}{5} \right)_{0}^{1}\] \[=\frac{1}{9}\left[ \frac{1}{4}{{\tan }^{-1}}\frac{1}{4}-\frac{1}{5}{{\tan }^{-1}}\frac{1}{5} \right]\]


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