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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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n是奇数，另外就是偶数——（n-1）就是能被2整除，(n+1) 能被4整除（n-1)(n+1)起码是8的倍数
连续三个整数的乘积是3的倍数 因为n不能被3整除，那么（n-1)(n+1)一定是3的倍数，
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