$cot\:x\:-\:\frac{sec\:x}{sin\:x}\left(1-2sin^2\:x\right)=\tan x$

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

$\left(x\cdot cos\left(x\right)-\sin\left(x\right)\right)^2$

$\lim_{x\to-\infty}\left(\frac{5x^2-2x+1}{x^2+72x+140}\right)$

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

$5n^2+19n+12$

$\frac{2x\:}{\:x+1}+\frac{8}{x-3}=0$