令 x = y = 0得:
f(1)
= f(0)×f(0) - f(0) - 0 + 2
= 1×1 - 1 - 0 + 2
= 2
令 y = 0得:
f(1) = f(x)×f(0) - f(0) -x + 2
2 = f(x) - 1 - x + 2
f(x) = x + 1
令 x = y = 0得:
f(1)
= f(0)×f(0) - f(0) - 0 + 2
= 1×1 - 1 - 0 + 2
= 2
令 y = 0得:
f(1) = f(x)×f(0) - f(0) -x + 2
2 = f(x) - 1 - x + 2
f(x) = x + 1