If k is an integer and 2 < k < 8, what is the value of k ?
(1) k is a factor of 30.
(2) k is a factor of 12.
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.
注意,不是prime factor而是 factor!
(1)3.5.6
(2)3,4,6
(1)((2)3,6也不充分
如何分解出全部的因数:第一步列出1,第二步列出所有质因数,第三步将所有质因数组合,包括两两相乘、三三相乘,一直到所有质因数的相乘(等于本身)。
因数的个数=1+C(n,1)+C(n,2)+……+C(n,n),如果因数里有m个相同的数字,减去包含相同数字的组合个数。
看错题目,不是prime factor而是 factor
3和6都有可能
k是公约数