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

  • question_answer
    \[\int_{{}}^{{}}{{{e}^{{{x}^{2}}}}x\ dx}\] is equal to [SCRA 1996]

    A)            \[{{e}^{{{x}^{2}}}}\]

    B)            \[\frac{1}{2}{{e}^{{{x}^{2}}}}\]

    C)            \[2{{e}^{{{x}^{2}}}}\]

    D)            \[\frac{{{e}^{{{x}^{2}}}}-{{x}^{2}}}{2}\]

    Correct Answer: B

    Solution :

                       \[\int_{{}}^{{}}{{{e}^{{{x}^{2}}}}.x\,dx}=\frac{1}{2}\int_{{}}^{{}}{(2x){{e}^{{{x}^{2}}}}dx}\]            \[=\frac{1}{2}\int_{{}}^{{}}{{{e}^{t}}dt}=\frac{1}{2}{{e}^{t}}=\frac{1}{2}{{e}^{{{x}^{2}}}}\],   (Put \[{{x}^{2}}=t\Rightarrow dt=2x\,dx)\].


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