$\left(x-13\right)\left(x-7\right)\left(x-5\right)\left(x-3\right)$

$\frac{\tan\left(0.1\right)}{0.1}$

$\:\left(m\:3-\:6m\:2-\:16m\:+\:63\right)\left(m\:-\:7\right)$

$\left(n^6\right)^8$

$\frac{d}{dx}\left(cos\left(xy\right)=xe^y\right)$

$\left(a-1\right)\left(a+1\right)-\left(a+1\right)^2-\left(a-1\right)^2+3a\left(a+6\right)$

$\left(7a^2+2a^3\right)\left(7a^2-2a^3\right)$