Exact differential equation problem

Find a function F(x,y) whose level curves are solutions to the differential equation $$( x^2 - 4xy )dx + x dy= 0$$

I am confused on how to solve this. The idea is to the use exact form to solve it but they don't come out to be exact. I got that

$$M = x^2 - 4xy$$ $$N = x$$

Taking the partial derivative of both does not come out to be exact. What else can I do to solve this?

Multiply your original equation by the integrating factor $\frac{1}{x}e^{-4x}$: $$(x^2-4y)e^{-4x}dx + e^{-4x}dy=0.$$ Then $M_y=-4e^{-4x}=N_x$, so this new (and equivalent) differential equation is exact, so you can solve it.