$\displaystyle (y^{4}-4xy)dx+(2xy^{3}-3x^{2})dy=0$
prove that this equation has an xy dependant integration coefficient
the condition i gave you gives you the integrating factor, if those constants exist, then the integrating factor is $\displaystyle u(x,y)=x^my^n,$ but on your question you were asked to show that your equation has a integrating factor which depends of $\displaystyle xy,$ so that will force that $\displaystyle m=n$ in order to have $\displaystyle u(x,y)=h(xy).$