4 2 3 5*x *y*-3*x *y
5*x^4*y*(-3)*x^2*y^3
6 4 -15*x *y
-15*x^6*y^4
1*(x + 0)*(y + 0)
(1*(x + 0))*(y + 0)
-15.0*x^6*y^4