x^2 + y^2 - 6x + 2y + 10 = 0
(x^2-6x+9(+(y^2+2y+1)=0
(x-3)^2+(y+1)^2=0
因为(x-3)^2≥0,(y+1)^2≥0
因此x-3=0,x=3
y+1=0,y=-1
那么x^2-y^2=9-1=8
8开三次方等于2