$3ab^2-5x^3y^4+6b^2a^2-7ab^2+12x^3y^4$

$-16^3$

$2\left(-\frac{1}{y}=-x^2+0\right)$

$\frac{2}{3}\left(\frac{1}{4}x-6\right)$

$\left(x^2+1\right)\frac{dy}{dx}+\:3xy=6$

$1225-36x^4$

$\frac{\cos^2\left(x\right)+\cos\left(x\right)-12}{\cos\left(x\right)-3}=\cos\left(x\right)+4$