$\frac{d^2}{dx^2}\left(2\cdot\cos\left(\frac{1}{2}x\right)\right)$

$\frac{dy}{dx}=\frac{\left(x^2+2\right)}{3y^2}$

$\left(4x^3+3xy+8y^2\right)\left(4x^3-3xy-8y^2\right)$

$2.5\left(4.2x\:+\:7.4y\right)\:-3.6\left(8x\:-\:4.5y\right)\:-\:\left(2.4x\:+\:6y\right)$

$\left(5y^{a+1}+4\right)\left(5y^{a+1}-15\right)$

$m^2+12m+36=\left(m+\right)^2$

$\left(2ab+1\right)\left(2ab-1\right)$