In fact ,you can say any nuber N，只要您能说出道理.比如

来源: 于 2010-09-08 08:25:37 [博客] [旧帖] [给我悄悄话] 本文已被阅读：次

令 f(1) = 1/2; f(2) = 1/4; f(3) = 1/4; f(4) = N,确定唯一的三次函数:
f(x) = a*x^3 + b*x^2 + c*x + d.