扫描二维码，直接登录
题库 / Prep2008E1-DS-3
How many different prime numbers are factors of the positive integer n ?
(1) Four different prime numbers are factors of 2n.
(2) Four different prime numbers are factors of n2.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
还没有题目讲解（毕出老师会陆续发布对官方考题的解读，请保持关注）。
（1）当2是n的一个质因子的时候，2n的different prime numbers和n的相等，因为2这个质因子在2n中重复了两次。
eg. n=2*3*5*7; 2n=2*2*3*5*7
当2不是n的一个质因子的时候，2n的different prime numbers比n多一个
eg. n=3*5*7; 2n=2*3*5*7
（2）n与n方个数个数应当相等
eg. n=2*3*5*7; n方=2*2*3*3*5*5*7*7
登录 或 注册 后可以参加讨论