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

  • question_answer
    \[\int_{{}}^{{}}{\frac{dx}{x+x\log x}=}\]    [MP PET 1993; Roorkee 1977]

    A)            \[\log (1+\log x)\]

    B)            \[\log \log (1+\log x)\]

    C)            \[\log x+\log (\log x)\]

    D)            None of these

    Correct Answer: A

    Solution :

                       \[\int_{{}}^{{}}{\frac{dx}{x+x\,\,\log x}}=\int_{{}}^{{}}{\frac{dx}{x(1+\log x)}}\]            Now putting \[1+\log x=t\Rightarrow \frac{1}{x}\,dx=dt,\] it reduces to            \[\int_{{}}^{{}}{\frac{dt}{t}}=\log (t)=\log (1+\log x)\].


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