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题库 / Prep2007E2-DS-162
If n is a positive integer and r is the remainder when n2 - 1 is divided by 8, what is the value of r ?
(1) n is odd.
(2) n is not divisible by 8.
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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看到偶数和奇数，就可以设偶数为2n,奇数为2n+1这样来做
当n为奇数的时候：n^2-1= 2n(2n+2)=4n(n+1) n和n+1两个连续整数肯定有一个是偶数，则可以被8整除
n不能被8除的时候，则因素厘米不含有2和4的因子，因此n^2不能被8整除，那么n^2-1就不好判断了
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