15年前做过的一道题# BrainTeaser - 大脑工作室b*m2007-07-17 07:071 楼定义域为非负整数集的函数f(n)满足1. f(m^2+n^2) = f(m)^2 + f(n)^22. f(1) = 1求证f(n) = n
l*z2007-07-17 07:075 楼easyf(2)=2f(2^0.5)=(f(2))^0.5 = 2^0.5F(3)= 1^2 + (2^0.5)^2 =3【在 f******y 的大作中提到】: 你先给大家show一下f(3)=3.
f*y2007-07-17 07:076 楼"定义域为非负整数集的函数f(n)"【在 l**z 的大作中提到】: easy: f(2)=2: f(2^0.5)=(f(2))^0.5 = 2^0.5: F(3)= 1^2 + (2^0.5)^2 =3
a*h2007-07-17 07:078 楼题目不是f(n^2)吗?怎么来了个f(n^0.5)了?【在 l**z 的大作中提到】: easy: f(2)=2: f(2^0.5)=(f(2))^0.5 = 2^0.5: F(3)= 1^2 + (2^0.5)^2 =3
b*m2007-07-17 07:0714 楼f(1)->f(2)->f(4)->f(5)->f(3^2+4^2), enjoy【在 b*****g 的大作中提到】: 一看就知道1^2+2^2=5: 3怎么凑或者反凑?
f*y2007-07-17 07:0719 楼in this way,you can show f(3)^2=9,but not f(3)=3.Am I right?【在 b*******m 的大作中提到】: f(1)->f(2)->f(4)->f(5)->f(3^2+4^2), enjoy
b*m2007-07-17 07:0720 楼yes, so you can add that condition to be non-negative. hehe【在 f******y 的大作中提到】: in this way,you can show f(3)^2=9,but not f(3)=3.Am I right?