$x^2\:-\:21\:x\:+20$

$\frac{8\cot^3\left(x\right)}{\csc\left(x\right)}$

$\int\cot^6\left(\frac{x}{2}\right)dx$

$\lim_{x\to-5}\left(\frac{x^2+3x-10}{2x^2+15x-25}\right)$

$4m^2+9=0$

$-4\cos x+8=\cos x+8$

$-\left|12+\left(-3\right)\right|-\left(-4\right)-5+6-\left(-4\right)$