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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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设n=2k+1, k为整数
(2k+1)²-1=4k²+4k=4k(k+1)
显然k与k+1一奇一偶，k*(k+1)是偶数
故n²-1能被8整除
k=0的时候呢，也就是n=1呢，0除以8余数是多少
好问题，我也是纠结这个然后选了E
0也没问题啊，0/8=0,余数也是0，算整除；
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