2 3 x *y - 36*y
x^2*y - 36*y^3
/ 2 2\ y*\x - 36*y /
y*(x^2 - 36*y^2)
1*(x + 6*y)*(x - 6*y)*(y + 0)
((1*(x + 6*y))*(x - 6*y))*(y + 0)
y*(x - 6*y)*(x + 6*y)
-36.0*y^3 + y*x^2