$\frac{1}{\cot\left(x\right)}-\frac{\sec\left(x\right)}{\csc\left(x\right)}=\cos\left(x\right)$

$\left(3b-20a+14\right).\left(7ab+15a\right)$

$\:-\:\left(-81\:+\:40\right)\:-\:3\left(\:25\:+35\right)$

$2\left(y-z\right)^2$

$\frac{z^{-5}}{z^3}$

$\lim_{x\to2}\left(\frac{\sqrt{x^2-4}}{x^2-4}\right)$

$-63-\left(-5\cdot14\right)$