(x+y)^2-3(x+y)=0 ①
x-y=1 ②
将①因式分解得：(x+y)(x+y-3)=0 ==>x+y=0或x+y-3=0
当x+y=0时,代入②中得：x=1/2 y=-1/2
当x+y-3=0时,代入②中得：x=2 y=1
即方程组的解为：x=1/2 y=-1/2 或x=2 y=1