I dont see how to make this into an I.F. format:
(3x^2y + 2xy + y^3)dx + (x^2 + y^2)dy = 0
Your equation $\displaystyle Pdx+Qdy$ satisfies:
$\displaystyle \dfrac{1}{Q}\left( \dfrac{\partial P}{\partial y}-\dfrac{\partial Q}{\partial x}\right)=3$
This means that the equation has an integrating factor that depends on $\displaystyle x$ .
Fernando Revilla
$\displaystyle 3=3+0x$
Fernando Revilla
$\displaystyle \dfrac{\mu'(x)}{\mu (x)}=3 \Rightarrow\log |\mu(x)|=\int 3\; dx\Rightarrow \ldots$
Fernando Revilla