$f\left(x\right)=\cos2x\ctan2x-8$

$\left(\frac{1}{4}m-\frac{2}{5}n\right)\left(-\frac{1}{4}m+\frac{2}{5}n\right)$

$\int\frac{50}{x[\left(3x+4\right)^{2}+9]}dx$

$\frac{x^3}{x^2-2x+4}$

$\frac{dy}{dx}+2y=4cos\left(2x\right)$

$\frac{dy}{dx}\left(\frac{3x+8}{5x-1}\right)$

$9x^2-80x-9$