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

  • question_answer
    The value of \[\int_{{}}^{{}}{\frac{{{x}^{3}}}{\sqrt{1+{{x}^{4}}}}\ dx}\] is                [SCRA 1996]

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

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

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

    D)            \[-\frac{1}{2}{{(1+{{x}^{4}})}^{\frac{1}{2}}}+c\]

    Correct Answer: C

    Solution :

    \[\int_{{}}^{{}}{\frac{{{x}^{3}}}{\sqrt{1+{{x}^{4}}}}\,dx}=\frac{1}{4}\int_{{}}^{{}}{\frac{4{{x}^{3}}}{\sqrt{1+{{x}^{4}}}}\,dx}\]           \[(\text{Put}\,1+{{x}^{4}}=t)\]                    \[=\frac{1}{4}\int_{{}}^{{}}{\frac{dt}{{{t}^{1/2}}}}=\frac{1}{4}\frac{{{t}^{-\frac{1}{2}+1}}}{-\frac{1}{2}+1}=\frac{1}{2}\sqrt{t}=\frac{1}{2}\sqrt{1+{{x}^{4}}}+c.\]


You need to login to perform this action.
You will be redirected in 3 sec spinner