x^2+y^2+6x-4=0.(1)
x^2+y^2+6y-28=0.(2)
(1)-(2):6x-6y=-24
x-y=-4
x=y-4.(3)
(3)代入(2):
(y-4)^2+y^2+6y-28=0
2y^2-2y-12=0
(y-3)(y+1)=0
y=3,或y=-1
代入(3):
x=3-4=-1,或x=-1-4=-5
所以x=-1,y=3
或x=-5,y=-1
x^2+y^2+6x-4=0.(1)
x^2+y^2+6y-28=0.(2)
(1)-(2):6x-6y=-24
x-y=-4
x=y-4.(3)
(3)代入(2):
(y-4)^2+y^2+6y-28=0
2y^2-2y-12=0
(y-3)(y+1)=0
y=3,或y=-1
代入(3):
x=3-4=-1,或x=-1-4=-5
所以x=-1,y=3
或x=-5,y=-1