$\left[-15+\left(-7\right)\right]\left(-8-11\right)$

$\sqrt{\left(5+2\sqrt{6}\right)\left(5-2\sqrt{6}\right)}$

$\frac{z^2}{4}+4+4y^4$

$16x^3y^3-8x^4y^5-24x^2y^2-40x^6y^4$

$100-17$

$\lim_{x\to-2}\left(\frac{x^2+8x+12}{x^2+6x-12}\right)$

$tan\left(\:x\right)+\frac{1}{tan\left(x\right)}=\frac{\csc\left(x\right)}{\cos\left(x\right)}$