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∫x9(4x2+1)6 dx\int \frac{x^9}{(4x^2+1)^6}\,dx is equal to:

[where c is an arbitrary constant]

Solution

✅ Correct Option: 4

Take x12x^{12} out of the denominator: the integrand becomes 1x3(4+1x2)−6\frac{1}{x^3}\left(4+\frac{1}{x^2}\right)^{-6}. Put u=4+1x2u = 4 + \frac{1}{x^2}, so dxx3=−du2\frac{dx}{x^3} = -\frac{du}{2}. The integral is −12∫u−6du=110(1x2+4)−5+c-\frac{1}{2}\int u^{-6}du = \frac{1}{10}\left(\frac{1}{x^2}+4\right)^{-5} + c.

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