x²+2xy+y²=9.(1)
(x-y)²-3(x-y)+2=0.(2)
由(1)得
(x+y)²=9
x+y=3或x+y=-3
由(2)得
(x-y-1)(x-y-2)=0
x-y=1或x-y=2
∴构成四个方程组
x+y=3且x-y=1 => 解得x=2,y=1
x+y=3且x-y=2 => 解得x=5/2,y=1/2
x+y=-3且x-y=1 => 解得x=-1,y=-2
x+y=-3且x-y=2 => 解得x=-1/2,y=-5/2