In Example 1.5 of Differential Equations Demystified, the equation is y' +2xy = x, and the author claims this is not separable. Now, what am I missing. I try the following.
1) dy/dx = x - 2xy
2) dy/dx = x(1-2y)
3) dy/(1-2y) = xdx
I guess one of those is invalid but I just...