解方程组:（1）x^2-xy+y^2=3 x^2+y^2-x-y=2

1）令a=x+y,b=xy则方程1化为：(x+y)²-3xy=3,即a²-3b=3,得b=a²/3-1方程2化为：(x+y)²-2xy-(x+y)=2,即a²-2b-a=2,代入b,得：a²-2a²/3+2-a=2即a²/3-a=0a(a/3-1)=0a=0,3故b=-1,2...