Find $\displaystyle \int{x^3\sqrt{4-x^2}\;dx}$
*use the substitution $u=4-x^2$
Find $\displaystyle \int{x^{-\frac{3}{2}}\sqrt{1-x}}\;dx$
*use the substitution $x=\cos^2{\theta}$
The following integrals come from the M.I.T. Integration Bee, an annual competition hosted by the Massachusetts Institute of Technology. You can view some matches here.
Level 1: (do not require Integration by Substitution or Integration by Parts) Don’t forget $+c$
$\displaystyle \int{\frac{x^2+1}{x+1}}dx$
$\displaystyle \int \frac{\sin^3 x + \sin^2 x - 2\sin x - 2}{\sin^2 x + 2\sin x + 1}\, dx$
$\displaystyle \int (\sin^6 x + \cos^6 x + 3\sin^2 x\cos^2 x)\,dx$
Level 2: (may require Integration by Substitution but not Integration by Parts) Don’t forget $+c$