$-39-\left(-13\right)$

$2p^2q\:+\:2p^2q^2\:+\:2pq^2\:$

$\lim_{x\to0}\left(\frac{x^2}{\cos\left(x-1\right)}\right)$

$\lim_{n\to0}\frac{\left(\sqrt{10n^2+7n+3}\right)}{n^2}$

$\lim_{x\to a}\left(\frac{cos\left(x\right)-\cos\left(a\right)}{x-a}\right)$

$\left(x+1\right)^3\left(3+2x\right)$

$\frac{d}{dx}\left(\ln\left(\cosh\left(6x+3\right)\right)\right)$