Definite Integration Question 89

Question 89

  1. The value of 014x3d2dx2(1x2)5dx is

(2014 Adv.)

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Answer:

Correct Answer: 91. (2)

Solution:

  1. PLAN Integration by parts

f(x)g(x)dx=f(x)g(x)dxddx[f(x)]g(x)dxdx

Given, I=014x3d2dx2(1x2)5dx

$$ =4 x^{3} \frac{d}{d x}\left(1-x^{2}\right)^{5}{ }{0}^{1}-\int{0}^{1} 12 x^{2} \frac{d}{d x}\left(1-x^{2}\right)^{5} d x $$

$$ \begin{aligned} & =4 x^{3} \times 5\left(1-x^{2}\right)^{4}(-2 x) \ & \quad-12\left[x^{2}\left(1-x^{2}\right)^{5}\right]{0}^{1}-\int{0}^{1} 2 x\left(1-x^{2}\right)^{5} d x \ & =0-0-12(0-0)+12 \int_{0}^{1} 2 x\left(1-x^{2}\right)^{5} d x \ & =12 \times-\frac{\left(1-x^{2}\right)^{6}}{6}{ }_{0}^{1}=120+\frac{1}{6}=2 \end{aligned} $$



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