it's the same procedure.
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!