解方程组x²-y²-2x-2y=0;x²+xy+y²-28=0

由(1)得(x+y)(x-y)-2(x+y)=0(x+y)(x-y-2)=0x+y=0 x-y-2=0它们与(2)可组成两个方程组x+y=0 x-y-2=0x²+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=4y=-2√7 y=2√7 y=-4 y=...