arthham

JEE Advanced 2010 · Integrals

The value(s) of ∫01x4(1−x)41+x2 dx\int_{0}^{1}\frac{x^{4}(1-x)^{4}}{1+x^{2}}\,dx is (are)

Answers: A. 227−π\frac{22}{7}-\pi

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The value(s) of ∫₀¹(x⁴(1-x)⁴)/(1+x²) dx is (are) I=∫01x4(1−x)41+x2 dxI = \int_0^1 \dfrac{x^4(1-x)^4}{1+x^2}\,dx To find: the value of I\text{To find: the value of } I 1. expand x4(1−x)41.\ \text{expand } x^4(1-x)^4 2. divide by 1+x22.\ \text{divide by } 1+x^2 3. integrate term by term on [0,1]3.\ \text{integrate term by term on } [0,1] (1−x)4=1−4x+6x2−4x3+x4(1-x)^4 = 1 - 4x + 6x^2 - 4x^3 + x^4 x4(1−x)4=x4−4x5+6x6−4x7+x8x^4(1-x)^4 = x^4 - 4x^5 + 6x^6 - 4x^7 + x^8 x4(1−x)4=(1+x2)(x6−4x5+5x4−4x2+4)−4x^4(1-x)^4 = (1+x^2)\big(x^6 - 4x^5 + 5x^4 - 4x^2 + 4\big) - 4 x4(1−x)41+x2=x6−4x5+5x4−4x2+4−41+x2\dfrac{x^4(1-x)^4}{1+x^2} = x^6 - 4x^5 + 5x^4 - 4x^2 + 4 - \dfrac{4}{1+x^2} I=[x77−4x66+5x55−4x33+4x]01−4 ⁣ ⁣∫01 ⁣ ⁣dx1+x2I = \left[\dfrac{x^7}{7} - \dfrac{4x^6}{6} + \dfrac{5x^5}{5} - \dfrac{4x^3}{3} + 4x\right]_0^1 - 4\!\!\int_0^1\!\!\dfrac{dx}{1+x^2} =17−23+1−43+4−4⋅π4= \dfrac{1}{7} - \dfrac{2}{3} + 1 - \dfrac{4}{3} + 4 - 4\cdot\dfrac{\pi}{4} =17−2+5−π=17+3−π=227−π= \dfrac{1}{7} - 2 + 5 - \pi = \dfrac{1}{7} + 3 - \pi = \dfrac{22}{7} - \pi I=227−π ⇒ option (1)\boxed{I = \dfrac{22}{7} - \pi \ \Rightarrow \ \text{option } (1)}

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