$\lim_{x\to0}\left(2\right)\left(\frac{8}{x^2-4}-\frac{x}{x-2}\right)$

$a^2+4a-21$

$f\left(x\right)=\left\{3x+7:-3<\:x<\:0,\:x^2-6x+7:0\le\:\:x\le\:4,\:-2x+7:4<\:x\le\:6\right\}$

$x\:+\:8y\:+\:10x$

$\frac{3x}{x^2+x-2}$

$\int\frac{1}{5\sqrt{x^2+\frac{2}{25}}}dx$

$x^2+16x+16=0$