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

$4mn\:+\:2m\:+\:6mn\:-\:9n$

$\left(x^2\right)\left(x^{\frac{2}{3}}\right)$

$2x^4+4x^2$

$9a^2-36b^2$

$\frac{d}{dx}\left(\frac{-y^3-3yx^2}{x\left(x^2+3y^2\right)}\right)$

$12+x^2+x$