JEE Main & Advanced Mathematics Definite Integration Question Bank Fundamental definite integration, Definite integration by substitution

  • question_answer
    \[\int_{\,0}^{\,3}{\,\frac{3x+1}{{{x}^{2}}+9}dx=}\]                                           [EAMCET 2003]

    A)                 \[\log (2\sqrt{2})+\frac{\pi }{12}\]           

    B)                 \[\log (2\sqrt{2})+\frac{\pi }{2}\]

    C)                 \[\log (2\sqrt{2})+\frac{\pi }{6}\]             

    D)                 \[\log (2\sqrt{2})+\frac{\pi }{3}\]

    Correct Answer: A

    Solution :

    \[\int_{0}^{3}{\frac{3x+1}{{{x}^{2}}+9}dx=\frac{3}{2}}\int_{0}^{3}{\frac{2x}{{{x}^{2}}+9}dx+}\int_{0}^{3}{\frac{dx}{{{x}^{2}}+9}}\]                                        \[=\left[ \frac{3}{2}\log ({{x}^{2}}+9)+\frac{1}{3}{{\tan }^{-1}}\left( \frac{x}{3} \right) \right]_{0}^{3}\]                           \[=\frac{3}{2}(\log 18-\log 9)+\frac{1}{3}\left( \frac{\pi }{4} \right)\]                                        \[=\frac{3}{2}\log 2+\frac{\pi }{12}=\log (2\sqrt{2})+\frac{\pi }{12}\].


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