$\frac{\left(r^2\right)^2}{r\:x\:2r}$

$\int-\frac{sec^2\left(2x\right)sin\left(2x\right)}{2}\:dx$

$\lim_{x\to0}\left(\frac{4x^3-8x^2}{2x^2}\right)$

$\lim_{x\to-1}\left(\frac{x^3-4x^2+5x+20}{x}\right)$

$\frac{dy}{dx}=-3x^{\frac{2}{5}}$

$6x^{2}y-3y^{2},\sin x,y=2$

$\frac{4x^2-4x+5}{2x-1}$