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标题: 请问一道Prep [打印本页]

作者: meckychen 时间: 2010-3-17 16:13
标题: 请问一道Prep
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.

How to analyze?
Thank you.

作者: 切尔西 时间: 2010-3-17 17:02
这个题应该选B吧
条件一：2n有四个质因数，可以是2*a*b*c也可以是2*2*a*b*c;这里假设a,b,c是n的质因数，所以无法确定
条件二：因为n^2有四个质因数，n*n质因数不会改变，所以条件二成立

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