$\int\frac{x^3}{\sqrt{81-x^2}}dx$

$\int\left(dx\div x^2\sqrt{9-x^2}\right)$

$\int\frac{x^2dx}{\left(9-x^2\right)^{\frac{3}{2}}}$

$\int\frac{dx}{x\sqrt{x^{2}+36}}$

$\int\frac{\left(x^2-16\right)^{\frac{3}{2}}}{x^3}dx$

$\int\frac{dx}{\sqrt{25-9x^2}}$

$\int\:\frac{x}{\sqrt{2x-5}}dx$

$\int\frac{x^5}{\sqrt{1+x^2}}dx$