已知长方形周长为20,两边长分别为x,y (均为整数）且满足x-y-x^2+2xy-y^2+2=0,求长方形的面积

x-y-x^2+2xy-y^2+2=0
(x-y)-(x-y)^2+2=0
(x-y)^2-(x-y)-2=0
(x-y-2)(x-y+1)=0
x=2+y
x=y-1
2x+2y=20
4+2y+2y=20
y=4
x=6
面积s=24
2y-2+2y=20
y=5.5（舍去）