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

$$2xy'=2y$$

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

$$\int_0^{\pi}16\sin^4xdx$$

$$\left(-36\right)\left(-6\right)\left(+2\right)$$

$$\frac{x^3+4x^2-21}{x^3-9x}$$

$$x^3-2x^2-3x$$