$\left(6x^2y^4z^7\right).\left(-2x^3\right)$

$\frac{6sin^2\left(t\right)}{tan^2\left(t\right)}=6cos^2\left(t\right)$

$x\left(x+13\right)=30$

$\left(2x-8\right)^2-\left(5x-1\right)^2$

$\frac{dy}{dx}y=\left(6x+9\right)^{-2}$

$xy'+2y=xcos\left(x^3\right)$

$\frac{x^{2}+3}{1}$