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

  • question_answer
    \[\int_{{}}^{{}}{\sqrt{x}{{e}^{\sqrt{x}}}\ dx=}\]  [Karnataka CET 2004]

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

    B)                 \[(2x-4\sqrt{x}+4){{e}^{\sqrt{x}}}+c\]

    C)                 \[(2x+4\sqrt{x}+4){{e}^{\sqrt{x}}}+c\]

    D)                 \[(1-4\sqrt{x}){{e}^{\sqrt{x}}}+c\]

    Correct Answer: B

    Solution :

                    \[I=\int_{{}}^{{}}{\sqrt{x}.{{e}^{\sqrt{x}}}}dx\]. Let \[x={{t}^{2}}\Rightarrow dx=2t\,dt\]                 \[\therefore I=2\int_{{}}^{{}}{{{t}^{2}}}\,.\,{{e}^{t}}dt\] Þ \[I=2({{t}^{2}}.{{e}^{t}}-2t{{e}^{t}}+2{{e}^{t}}]+c\]                 Þ \[I=\frac{1}{\sqrt{2}}\log \left| \tan \left( \frac{x}{2}+\frac{3\pi }{8} \right)\, \right|+c\]                 i.e., \[I={{e}^{\sqrt{x}}}[2x-4\sqrt{x}+4]+c\].


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