The positive integer k has exactly two positive prime factors, 3 and 7. If k has a total of 6 positive factors, including 1 and k, what is the value of k?
1) 3^2 is a factor of k.
2) 7^2 is NOT a factor of k
答案是D，跪求好心人解释....作者: angelsgx 时间: 2011-7-2 06:41
k= 3^n * 7^m
(n+1)(m+1)=6
n=2, m=1
or
m=2, n=1
1) n=2, then you can get k
2) m=/=2, then you can still get the value of k, which is the same as the one you get from 1)作者: flyfairy019 时间: 2011-7-3 21:12
