求一道数学题意和题解

jessiedai

The function f is defined for all positive integers n by the following rule: f(n) is the number of positive integers each of which is less than n and has no positive factor in common with n other than 1. If p is any prime number than f(p)=

A. p-1

B. p-2

C. (p+1)/2

D. (p-1)/2

E. 2

正确答案是A.

请高人指点下,这道题意是什么?怎么解呢? 多谢拉!

jessiedai

 

谢谢你