$$(axy^2+by)dx+(bx^2y+ax)dy=0$$
I have asked this question before too, but i wish to know the method for evaluating the integrating factor which is $\dfrac {1} {(a-b)(x^2y^2-xy)}.$
So far i know:
$M(x,y)dx + N(x,y)dy=0$ is said to be a perfect differential when
$\frac{\partial (M(x,y))}{\partial y}=\frac{\partial (N(x,y))}{\partial x}$.
In this case the equation is not exact and integrating factor is multiplied to make the differential equation exact.
Is there any other method to solve this differential equation?