Find an integrating factor for:
xdy - (y + x^2 + 9y^2)dx = 0
P(x,y)dx + Q(x,y)dy = 0
Δμ = μyP - μxQ.
where μ is the integrating factor.
The Attempt at a Solution
well, I don't know what I should do. I can use the formula I wrote but that would lead to solving a PDE. any ideas?