In one of the examples in the Differential Equations for Dummies Workbook (Holzner), you are asked to use an integrating factor to solve $ \frac{dy}{dx} +2y =4 $
My question is, is this the most efficient way to solve it? Can't I also solve it by separating the $y$, turning the equation into $\frac{1}{2-y}\frac{dy}{dx} = 2$. Are there other ways? How do you quickly determine what will be the quickest way?