x²+2xy+y²=4x²-xy-y²=0方程1化为(x+y)²=4,得x+y=2或x+y=-2将x=2-y代入方程2得：4-4y+y²-2y+y²-y²=0,得y²-6y+4=0,得y1=3+√5,y2=3-√5; 从而x1=-1-√5,x2=-1+√5;将x=-...