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∫131(x−x3)13x4dx=\int_{\frac{1}{3}}^{1} \frac{(x - x^3)^{\frac{1}{3}}}{x^4} dx =

Solution

✅ Correct Option: 3

Rewrite integrand: (x−x3)1/3x4=x1/3(1−x2)1/3x4\frac{(x-x^3)^{1/3}}{x^4} = \frac{x^{1/3}(1-x^2)^{1/3}}{x^4}. Factor as 1x3(1x2−1)1/3\frac{1}{x^3}\left(\frac{1}{x^2}-1\right)^{1/3}.

Let t=1x2−1t = \frac{1}{x^2}-1, so dt=−2x3dxdt = -\frac{2}{x^3}dx. Limits: x=13→t=8x=\frac{1}{3} \to t=8; x=1→t=0x=1 \to t=0.

I=12∫08t1/3 dt=12⋅34⋅84/3=38⋅16=6I = \frac{1}{2}\int_0^8 t^{1/3}\,dt = \frac{1}{2}\cdot\frac{3}{4}\cdot 8^{4/3} = \frac{3}{8}\cdot 16 = 6.

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