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

$\left(\frac{x^2}{\left(4x^2+12\right)^3}\right)$

$\left(-\frac{3}{4}\right)\cdot\frac{1}{2}\cdot\left(-\frac{5}{3}\right)\cdot\frac{8}{5}$

$\left(3x-2y\right)\left(5x-2y\right)$

$x^2\left(-8x^2-3x\right)$

$2x^2+36x+170$

$\lim_{x\to\infty}\left(8xe^{-x}\right)$