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If ∫x3 dx1+x2=a(1+x2)3/2+b1+x2+c\displaystyle\int\dfrac{x^3\,dx}{\sqrt{1+x^2}} = a(1+x^2)^{3/2}+b\sqrt{1+x^2}+c, where 'C' is an arbitrary constant, then the value of aa and bb are

Solution

✅ Correct Option: 4

Put u=1+x2u=1+x^2, so x dx=du2x\,dx=\dfrac{du}{2} and x2=u−1x^2=u-1. The integral becomes 12∫(u1/2−u−1/2)du=13u3/2−u1/2\dfrac12\displaystyle\int\left(u^{1/2}-u^{-1/2}\right)du=\dfrac13u^{3/2}-u^{1/2}. Comparing, a=13a=\dfrac13 and b=−1b=-1.

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