$-\frac{\cos^2\left(x\right)}{\sin\left(x\right)}=2\sin\left(x\right)-\csc\left(x\right)$

$\sqrt[2]{3x^2+6}-3$

$4x^2+12^2+625$

$\frac{x^3-8}{x^3-27}\cdot\frac{x^2-3x+9}{x^2+2x+4}$

$-2\left(x-8\right)\ge2x$

$4xy+2y^2+2x^2+2x+2y-2\left(x+y\right)^2$

$\sqrt[2]{\frac{4}{9}\cdot\frac{36}{16}}$