Question

若(-x+1)/(x+1)的值为整数,求符合条件的整数x的值

Answer 1

(-x+1)/(x+1) = (-x-1+2)/(x+1) = -1 + 2/(x+1)

也就是说,要求 2/(x+1) 为整数,很容易看出：

x = -3,-2,0 ,1

可使 2/(x+1) 是整数,也就是 (-x+1)/(x+1) 是整数.