$2\sqrt{5}+\sqrt{5}-4\sqrt{5}$

$\left(-\:2\right)\:\left(6\right)\:\left(-\:3\right)\:\left(-\:1\right)\:$

$\left(2h^3+4\right)\left(2h^3-9\right)$

$55gn^2n^3x+110m^2n^3x^2$

$\left(4x^2+3x\right)\left(x-2\right)$

$\sqrt{\frac{y^4}{4}}$

$\frac{\cos^2x}{\csc^2x}=\frac{\sin^2x}{\sec^2x}$