$\frac{x+4}{x^2+8x+12}$

$\frac{dy}{dx}x^2=\left(1+x\right)\left(1-x\right)\left(1+y^2\right)$

$2\sec^2\left(x\right)-1=\frac{1+\sin^2\left(x\right)}{\cos^2\left(x\right)}$

$3\:x^3\:+\:5x^2y$

$xa+1-3xa-2$

$2x^2y-5x^2y$

$\sec^2\left(x\right)\:\cot^2\left(x\right)-\cos^2\left(x\right)\:\csc^2\left(x\right)=1$