由(1)得 (x+y)(x-y)-2(x+y)=0 (x+y)(x-y-2)=0 x+y=0 x-y-2=0 它们与(2)可组成两个方程组 x+y=0 x-y-2=0 x²+xy+y²-28=0 x²+xy+y²-28=0 解这两个方程组得 x=2√7 x=-2√7 x=-2 x=4 y=-2√7 y=2√7 y=-4 y=2
