$\lim_{x\to4}\left(\frac{x^2+2x-15}{x-3}\right)$

$\left(\frac{1}{2}m+n\right)\left(\frac{1}{2}-2n\right)$

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

$\left(-4n^2+2mn+3m^2\right)\left(2m^2+6n^2-5mn\right)$

$\int_{-3}^35e^{5x}dx$

$20\left(x^2-y^2\right)$

$\int\frac{1}{x^2-4x}dx$