把x=8-y代入(x-y)(x-y-2)+1=0得：
(8-y-y)(8-y-y-2)+1=0
4(4-y)(3-y)+1=0
4y^2-28y+48+1=0
4y^2-28y+49=0
(2y-7)^2=0
得：2y-7=0 即：y=3.5
所以：x=8-y=8-3.5=4.5