Math Help - ODE Proof

1. ODE Proof

Hello,

I need to prove something related to 1st order exact equations. Here's the question:
Show that the diff. equation M+Ny'=0 has an integrating factor which is a function of z=x+y only if and only if

(dM/dy - dN/dx)/(M-N)

is a function of z only.

I'd just like to get a tip on how to start the problem. Thank you!

http://www.mathhelpforum.com/math-he...xy-158337.html

it's the same procedure.

3. Thank you very much!

4. Aw, I'm sorry but I don't get it... I'm actually pretty bad at proofs. Honestly I have no idea what to do with the link you provided... Thanks.

5. read it carefully, i can't help ya now because i'm going to bed.

6. I did lol, but when I'm dealing with too many symbols and unknowns, I have a real hard time calculating something that makes sense. Sorry I'm that bad with proofs...