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

  • question_answer
    \[\int_{{}}^{{}}{\frac{t}{{{e}^{3{{t}^{2}}}}}\ dt=}\] [MP PET 1997]

    A)            \[\frac{1}{6}{{e}^{3{{t}^{2}}}}+c\]

    B)            \[-\frac{1}{6}{{e}^{3{{t}^{2}}}}+c\]

    C)            \[\frac{1}{6}{{e}^{-3{{t}^{2}}}}+c\]

    D)            \[-\frac{1}{6}{{e}^{-3{{t}^{2}}}}+c\]

    Correct Answer: D

    Solution :

                       \[I=\int_{{}}^{{}}{t\,.\,{{e}^{-3{{t}^{2}}}}dt}\]            Put \[-3{{t}^{2}}=z\Rightarrow -6t\,dt=dz\Rightarrow t\,dt=\frac{-1}{6}\,dz\]            \[\therefore \,\,\,I=-\frac{1}{6}\int_{{}}^{{}}{{{e}^{z}}dt}=\frac{-{{e}^{z}}}{6}+c=-\frac{{{e}^{-3{{t}^{2}}}}}{6}+c.\]


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