Find a point on the curvex^{3}+y^{3}= 5xy

other than the origin at which the tangent line is horizontal.

Here's what i got so far...

dy/xy = (5y-3x^2)/(3y^2-5x)

solved for y... y=3x^2/5

I have to plug y back into the initial equation right? I keep getting a wrong value .. I'm getting (250/27)^1/3. Can someone tell me what I did wrong and how i can get the right answer?!