$\frac{\left(x^2+2x-3\right)}{\left(x^2+3x-4\right)}$

$cos\:\left(x\right)=1-cos\left(x\right)$

$\frac{d^2}{dx^2}\left(x\cdot\cos\left(x\right)\right)\frac{6x^2}{2x^3+y}$

$\frac{y^2+3y-11}{y+5}$

$\frac{d}{dx}\left(c+x+f\left(x\right)\right)^2$

$\frac{\left(x+3\right)+\left(x-1\right)}{\left(x+1\right)}$