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!
我的理解:
f(n)=小于n的正整数,但是这些正整数不包括于n相差1的因素
如果p为质数,因素只有1和p本身,
所以f(p)=p-1
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