$\frac{-28+28}{-16-4-12}$

$\lim_{x\to2}\left(\frac{x^2-x-2}{x^2+2x}\right)$

$\frac{x^2+5x+7}{x+3}$

$4x^2-12xy+16y^2$

$\left(\sqrt[3]{\left(5^{10}\right)\cdot\left(5^4\right)^2}\right)^{\frac{1}{6}}$

$2\log\left(x+2\right)+\log\left(x+1\right)$

$a^2\:-\:\frac{2a}{7}\:+\:n$