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 then f(p) =
(A) p - 1
(B) p - 2
(C)
(D)
(E) 2
答案是A.看得云山雾里的。小于p和它互质的整数。然后就搞不懂了？ 谢谢大家啦！！！
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
这句话我的理解是： f(n)就是小于n 且与n 互质的数 的个数， 因为是the number of 嘛 。
然后现在随便取个质数p 只要比他小的数应该都是和它互质的吧。。 比p小的integer有p-1个， 所以f(p)就是p-1， p-1就是比质数p小的所有数的个数
不知道我这样说对不对？
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发表于 2014-1-8 12:17:51
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