$\left(5m-3n\right)\left(m^2-mn+n^2\right)$

$cot^2xsec^2x=cot^2x+1$

$\frac{8d^2}{2d}$

$\left(4mn-6mn+2y\right)\left(5y-3mn\right)$

$\lim_{x\to2}\left(2x^2+3x-2\right)$

$\lim_{x\to0}\left(\frac{x^2-42x+441}{sin^2\left(\pi x\right)}\right)$

$\frac{dy}{dx}=\frac{sen4x}{cos2x}$