x^2+y^2-4x+6y+13=0,则xy=?

问题描述:

x^2+y^2-4x+6y+13=0,则xy=?

x^2+y^2-4x+6y+13=0
x^2-4x+4+y^2+6y+9=0
(x-2)^2+(y+3)^2=0
x=2,y=-3
xy=-6

(x-2)^2+(y+3)^2=0
x-2=0且y+3=0
x=2,y=-3
xy=-6

x^2+y^2-4x+6y+13=0
x^2-4x+4+y^2+6y+9=0
(x-2)^2+(y+3)^2=0
x=2
y=-3
xy=-6