$\left(+2\right)\:+\:\left(-3\right)\:+\:\left(-4\right)\:-\:\left(-1\right)\:$

$-\left(x-7\right)\left(x-2\right)$

$\lim_{x\to10}\left(\left(x-10\right)\cdot\frac{e^{-x}}{x^3-20x^2+125x-250}\right)$

$\lim_{x\to0}\left(\frac{2e^x-2\:+x\cos\left(x\right)}{sin^2x\:-3x}\right)$

$x^2+12x-13=0$

$16x^2-y^2$

$\frac{-24x^3y}{12xy}$