$\int\left(\frac{\cos^2\left(x\right)-\sin^2\left(x\right)}{\cos^2\left(x\right)}\right)dx$

$\frac{x^2+x-6}{x-2}$

$3^2\left(15+5\right)^2+2^3\left(15-5\right)^4$

$\frac{x-3}{x+4}=\frac{-2x-1}{x+4}+3$

$2x+y-z=20$

$\int\frac{1}{\cos^{2}\left(x\right)\tan\left(x\right)}dx$

$16xydx=\left(-8x^2+8y^2\right)dy$