$\frac{\left(x^3-2x^2-4x-8\right)}{15x-30}$

$-2\left(-3-3x\right)+1$

$\lim_{x\to0}\left(\frac{x^2-\arctan\left(x\right)^2}{\sin^2\left(x\right)}\right)$

$\frac{d^2}{dx^2}\left(x\cos\left(x+2\right)^2\right)$

$3a-\left(-2a+3b\right)+2a+\left(5a+8b\right)$

$\sqrt{12x^3y}+\sqrt{75xy^3}$

$121c^4-\:1$