x2+y2+2xy=9(x+y)²=9x+y=3或-3(x-y)2-3x+3y+2=0(x-y)²-3(x-y)+2=0(x-y-1)(x-y-2)=0x-y=1或2所以组成4个方程组x+y=3,x-y=1x+y=3,x-y=2x+y=-3,x-y=1x+y=-3,x-y=2所以x=2,y=1x=5/2,y=1/2x=-1,y=2x=-1/2,y=-5/...