$\frac{d^2}{dx^2}\left(-6x^8-9\right)$

$\frac{d^2y}{d^2x}\left(x^2\:+\:xy\:+\:y^2\:=\:6\right)$

$\left(-7.72\right)\cdot0.789$

$\frac{\sin^2\left(x\right)}{tan\left(x\right)}$

$9x^{10}\cdot5x^{-4}$

$-5x^{2}+5\left(5x-4\right)$

$5\sin\:^2\left(\theta\:\right)-2\cos\:\left(\theta\:\right)=0$