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题库 / Prep2007E1-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 ~$n^2$~.
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.
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问题：没想到n有4个质因数的可能性（含有2），武断（先入为主）的认为n只有3个质因数的可能性。
对策：记住两个不同的数的乘积，分别有重叠的质因数可能性存在。
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