$2x^2+3x-4-x^2+x+x$

$x-x^{-1}=2$

$\frac{1-\frac{1}{cos\left(x\right)}}{tan\left(x\right)}=\frac{cos\left(x\right)}{sin\left(x\right)}$

$\frac{16x^3+4x^2}{4x^2}$

$\frac{x}{3}^3+2$

$\lim_{x\to4}\left(\frac{\tan\left(9x\left(x-4\right)\right)}{x-4}\right)$

$x^2yz\:+\:3xy^2z\:-\:2xyz^2\:-\:3xy^2z\:+\:xyz^2\:-\:x^2yz$