KVPY Sample Paper KVPY Stream-SX Model Paper-2

  • question_answer
    \[\int{\frac{dx}{{{x}^{2}}\,{{({{x}^{5}}+1)}^{4/5}}}}\] equals:

    A) \[c+\frac{\sqrt[5]{1+{{x}^{5}}}}{4x}\]                       

    B) \[c-\frac{\sqrt[5]{1+{{x}^{5}}}}{x}\]

    C) \[c-\frac{\sqrt[5]{1+{{x}^{5}}}}{5x}\]             

    D) \[c+\frac{\sqrt[5]{1+{{x}^{5}}}}{x}\]

    Correct Answer: B

    Solution :

    \[I=\int{\frac{dx}{{{x}^{6}}{{(1+{{x}^{-\,5}})}^{4/5}}}}=\int{\frac{{{x}^{-\,6}}\,\,dx}{{{(1+{{x}^{-\,5}})}^{4/5}}}}\]
    Put \[{{x}^{-\,5}}=t\]
    \[\frac{-\,5}{{{x}^{6}}}\,\,dx=dt\]
    \[\frac{-1}{5}\int{\frac{dt}{{{(1+t)}^{4/5}}}}=-\frac{1}{5}{{(1+t)}^{1/5}}+\]
    \[c=-\frac{1}{5}{{(1+{{x}^{-\,5}})}^{1/5}}+c\]


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