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∫1/31(x−x3)1/3x4dx\int_{1/3}^{1} \frac{(x-x^3)^{1/3}}{x^4} dx equals

Solution

✅ Correct Option: 3

Write (x−x3)1/3=x(1x2−1)1/3(x-x^3)^{1/3}=x\left(\frac{1}{x^2}-1\right)^{1/3}, so the integrand becomes 1x3(1x2−1)1/3\frac{1}{x^3}\left(\frac{1}{x^2}-1\right)^{1/3}.

Put u=1x2−1u=\frac{1}{x^2}-1, so du=−2x3dxdu=-\frac{2}{x^3}dx; limits go from u=8u=8 to u=0u=0.

Integral =12∫08u1/3du=12⋅34⋅84/3=38×16=6=\frac12\int_0^8 u^{1/3}du=\frac12\cdot\frac34\cdot8^{4/3}=\frac38\times16=6.

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