Tough differential equation Hello! I'm having real trouble with this differential equation. I don't want you to solve it for me. Just give me a hint what I should do. (1+7x+6y+3x^2+4xy+5y^2)dx+2(1+2x+5y)dy=0 Obviously it is not exact. But I'm trying to find an integrating factor.. May be I should use another technique.