# Partial differential

1. Jul 13, 2006

### the_edge

Hello, I'm new at these equations so I need help. I'm not able to solve this partial differential equation, if there is somebody who can help me do it plzz...

http://galeb.etf.bg.ac.yu/~ii030168d/problem/problem.GIF [Broken]

OK, it begins like this:

http://galeb.etf.bg.ac.yu/~ii030168d/problem/problem1.GIF [Broken]

But I don't know what to do next... This problem is from exam on my faculty. (I havent pass)

I would appreciate any help...

Last edited by a moderator: May 2, 2017
2. Jul 14, 2006

### arildno

Well, the first equation may be rewrittent as a ratio between the differentials of x and y as follows:
$$\frac{dy}{dx}=\frac{x-y-x^{2}y}{x+y+xy^{2}}$$
I'm not sure if this is analytically solvable, though..

3. Jul 14, 2006

### arildno

You MIGHT try changing of variables u=x+y, v=x-y; possibly, that will simplify the expressions.

4. Jul 16, 2006

### the_edge

Sorry I made a mistake, problem is next:

dx/(x+y-xy^2) = dy/(x^2y-x-y) = dz/(z(y^2-x^2))

Maybe now there is solution. Those changes can't help, they wouldnt simplify the expression, but thanks...

Last edited: Jul 16, 2006