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

$\left(xy^3+3z\right)^2$

$\left(x+2y+4\right)dx+\left(2x+3y+7\right)dy=0$

$\left(3x+2x^2\:+7\right)\cdot\left(4x-2x^2+3\right)$

$12y^2+6xy-4x^2$

$\left(x-15\right)\left(x+15\right)$

$\frac{\sec\left(x\right)}{\sin\left(x\right)}-\sec\left(x\right)\sin\left(x\right)$