# Thread: Difficult first order D.E

1. ## Difficult first order D.E

I'm trying to solve dy/dx = (-y+xy) / (x-xy) using a change of variables but can't seem to find a substitution that works. Since the equation isn't homogenous u=y/x won't work. I've tried u=xy, u=-y+xy and u=x-xy all to no avail! Does anyone have a suggestion?

Many Thanks

2. It's separable.

3. Originally Posted by Ackbeet
It's separable.
How can it be separable when x and y appear in both the numerator and denominator? :S

Edit: I now realise all I have to do is factorise top and bottom. I should have spotted this!

4. Right. There you go.