3.196-!-item-!-187;#058&000141 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. -------------------------------------------------------------------------------------------------------------------------------------------------------- 【答案】B 【思路】 (1)如果2n=2.3.5.7的話 n的prime factor為3.5.7=>三個 如果2n=.3.5.7的話 n的prime factor為2.3.5.7=>四個 ,不充分 (2) ,a,b,c,d不管是幾次方,都可以確定質數只有四個,充分
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发表于 2011-7-29 01:49:00
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