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

  • question_answer
    \[\int_{{}}^{{}}{{{x}^{5}}.{{e}^{{{x}^{2}}}}dx=}\]

    A)                 \[\frac{1}{2}{{x}^{4}}{{e}^{{{x}^{2}}}}-{{x}^{2}}{{e}^{{{x}^{2}}}}+{{e}^{{{x}^{2}}}}+c\]     

    B)                 \[\frac{1}{2}{{x}^{4}}{{e}^{{{x}^{2}}}}+{{x}^{2}}{{e}^{{{x}^{2}}}}+{{e}^{{{x}^{2}}}}+c\]

    C)                 \[\frac{1}{2}{{x}^{4}}{{e}^{{{x}^{2}}}}-{{x}^{2}}{{e}^{{{x}^{2}}}}-{{e}^{{{x}^{2}}}}+c\]      

    D)                 None of these

    Correct Answer: A

    Solution :

                    Put \[{{x}^{2}}=t\Rightarrow 2x\,dx=dt,\] then                 \[\int_{{}}^{{}}{{{x}^{5}}{{e}^{{{x}^{2}}}}dx}=\frac{1}{2}\int_{{}}^{{}}{{{t}^{2}}{{e}^{t}}dt}=\frac{1}{2}\left[ {{e}^{t}}{{t}^{2}}-2\int_{{}}^{{}}{t{{e}^{t}}dt} \right]+c\]                     \[=\frac{{{t}^{2}}{{e}^{t}}}{2}-\left[ t{{e}^{t}}-{{e}^{t}} \right]+c=\frac{1}{2}{{x}^{4}}{{e}^{{{x}^{2}}}}-{{x}^{2}}{{e}^{{{x}^{2}}}}+{{e}^{{{x}^{2}}}}+c.\]


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