JEE Main & Advanced JEE Main Solved Paper-2015

  • question_answer
    The integral\[\int_{{}}^{{}}{\frac{dx}{{{x}^{2}}{{\left( {{x}^{4}}+1 \right)}^{{}^{3}/{}_{4}}}}}\]equals: [JEE Main Solved Paper-2015 ]

    A) \[-{{\left( {{x}^{4}}+1 \right)}^{\frac{1}{4}}}+c\]

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

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

    D) \[{{\left( {{x}^{4}}+1 \right)}^{\frac{1}{4}}}+c\]

    Correct Answer: B

    Solution :

    \[I=\int_{{}}^{{}}{\frac{dx}{{{x}^{5}}{{\left( 1+\frac{1}{{{x}^{4}}} \right)}^{{}^{3}/{}_{4}}}}}\] Let \[1+\frac{1}{{{x}^{4}}}={{t}^{4}}\] \[\frac{-4}{{{x}^{5}}}dx=4{{t}^{3}}dt\] \[I=\int_{{}}^{{}}{-\frac{{{t}^{3}}dt}{{{t}^{3}}}}=-t+c\] \[=-{{\left( \frac{{{x}^{4}}+1}{{{x}^{4}}} \right)}^{{}^{1}/{}_{4}}}+c\]


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