KVPY Sample Paper KVPY Stream-SX Model Paper-4

  • question_answer
     \[\int{\frac{{{x}^{3}}dx}{\sqrt{1+{{x}^{2}}}}}\] equals -

    A) \[\frac{{{(1+{{x}^{2}})}^{3/2}}}{3}\sqrt{1+{{x}^{2}}}+c\]

    B) \[{{x}^{2}}\sqrt{1+{{x}^{2}}}-\frac{1}{3}{{(1+{{x}^{2}})}^{3}}=c\]

    C) \[\frac{1}{3}{{x}^{2}}\sqrt{1+{{x}^{2}}}-\frac{2}{3}{{(1+{{x}^{2}})}^{3}}+c\]

    D) none of these

    Correct Answer: C

    Solution :

    [C]
    \[1+{{x}^{2}}={{t}^{2}}\]
    \[\Rightarrow I=\int{({{t}^{2}}-1)dt=\frac{{{t}^{3}}}{3}}-t\]
    \[=\frac{{{(1+{{x}^{2}})}^{3/2}}}{3}-\sqrt{1+{{x}^{2}}}\]
    \[=\frac{(1+{{x}^{2}})\sqrt{1+{{x}^{2}}}}{3}-\sqrt{1+{{x}^{2}}}(1+{{x}^{2}}-{{x}^{2}})\]
    \[=\frac{1}{3}{{x}^{2}}\sqrt{1+{{x}^{2}}}-\frac{2}{3}{{(1+{{x}^{2}})}^{3/2}}\]


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