$\sqrt[3]{81x^3y^4}$

$\lim_{n\to9}\left(\frac{x-9}{x^2-81}\right)$

$7x^2+10=5x$

$16x^2\:-\:8x+1=0$

$\cos\left(x\right)\left(\sin\left(x\right)^2-\cos\left(x\right)^2\right)\sec\left(x\right)-\cos\left(x\right)^2$

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

$\lim_{x\to4}\frac{\left|4-x\right|}{16-x^2}$