$\sec^22x-1=\tan^22x$

$y\:=\:x^2\:\:;\:x\:=\:2,x\:=\:4$

$\left(1-a^2\right)-\left(9n^2-6an\right)$

$9u-11u$

$-3m+15sim=3$

$\lim_{x\to0}\:ln\left(1+\frac{2}{x}\right)\cdot\frac{x}{2}$

$\left(\frac{x^{-2}y^{-3}}{x^{3}y^{2}}\right)\cdot[\frac{\left(y^{3}x^{-3}\right)^{-3}}{x^{2}y^{3}}]^{-2}$