(x-y)^2 - (x-y) =2
===> (x-y-1)(x-y)=2 将 x=8-y 带入
(8-2y-1)(8-2y)=2 ==> (8-2y-1)(4-y)=1 由于Y为整数,(8-2y-1)和(4-y)也都为整数,两个整数相乘要 等于1 ,必然 (8-2y-1)和(4-y)都为1,或者都为-1.
为1时 y=3 ,x=5 ,为-1时,不成立