Math Help - differential equation

1. differential equation

(dy/dx) + x/y^3 = -3y/x how do i solve this?

2. Originally Posted by crafty
(dy/dx) + x/y^3 = -3y/x how do i solve this?
Standard form

$\frac{dy}{dx} + \frac{3y}{x} = - \frac{x}{y^3}$

Multiply by $y^3$

$y^3 \frac{dy}{dx} + \frac{3y^4}{x} = - x$

and make the substitution $u = y^4$. The equation will become linear!