$18x-11x-7x-20ab+11ab$

$\int\left(\frac{e^x+e^{-x}}{e^x-e^{-x}}\right)\:dx$

$\frac{dy}{dx}+y=\cos\left(e^x\right)$

$\left(3x+8x^2\right)+\left(x^2-x+8\right)$

$-13-\left(8-19\right)$

$\lim_{x\to\infty}\left(\frac{\sqrt{4+10x^2}}{\left(3+10x\right)}\right)$

$\frac{3x^3-x+1}{x+3}$