$13-\left(-25\right)$

$\left(x-1\right)\left(x+h-1\right)$

$-\frac{1}{2}\left(16-8x\right)$

$\left(2x^{2m}+y^{5n}\right)\left(2x^{2m}-y^{5n}\right)$

$6x+5=-67$

$\frac{x^2-9}{6x^3-42x^2}.\frac{x^2-4x-21}{2x+6}$

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