(x+y)²=25,(x-y)²-3(x-y)+2=0
所以x+y=5或-5 (x-y-1)*(x-y-2)=0
x+y=5或-5,x-y=1或2
解得x=3,y=2或x=7/2,y=3/2或x=-2,y=-3或x=-3/2,y=-7/2.