$\lim_{x\to0}\left(\frac{tan20x}{sin4x}\right)$

$\frac{81m^6n^4-49m^2n^2}{gm^3n^2-7mn}$

$\left(-3-2x\right)^2$

$\sqrt{x^{-2}+x^{-10}+x^{-6}}$

$2\left|3\right|+15$

$a\:\left(x\:+\:10\right)\:+\:b\:\left(x\:+\:10\right)\:-\:c\:\left(x\:+10\right)$

$\frac{dx}{dy}=2\left(5-x\right)\left(8-x\right)$