JEE Main & Advanced Mathematics Indefinite Integrals Question Bank Integration by Parts

  • question_answer
    \[\int_{{}}^{{}}{(1-{{x}^{2}})\log x\ dx=}\]               [DSSE 1982]

    A)                 \[\left( x-\frac{{{x}^{3}}}{3} \right)\log x-\left( x-\frac{{{x}^{3}}}{9} \right)+c\]

    B)                 \[\left( x-\frac{{{x}^{3}}}{3} \right)\log x+\left( x-\frac{{{x}^{3}}}{9} \right)+c\]

    C)                 \[\left( x+\frac{{{x}^{3}}}{3} \right)\log x+\left( x+\frac{{{x}^{3}}}{9} \right)+c\]

    D)                 None of these

    Correct Answer: A

    Solution :

                    \[\int_{{}}^{{}}{(1-{{x}^{2}})\log x\,dx}=\int_{{}}^{{}}{\log x\,dx}-\int_{{}}^{{}}{{{x}^{2}}\log x\,dx}\]                                                 \[=x(\log x-1)-\frac{{{x}^{3}}\log x}{3}+\frac{{{x}^{3}}}{9}+c\]                                                 \[=\left( x-\frac{{{x}^{3}}}{3} \right)\log x-\left( x-\frac{{{x}^{3}}}{9} \right)+c.\]


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