DS: If n is a positive integer, is n^3-n divisible by 4? 1 n=2k+1, where k is an integer 2 n^2+n is divisible by 6 答案是A,我不知道是怎么整出来的？我将n=2k+1带入n^3-n好像也的不出什么结果来……
DS:if K is a positive integer, is k the square of an integer? 1 k is diviible by 4 2 k is divisible by exactly 4 different prime numbers. 答案选E 我想选的是B，因为我觉得2能证明k肯定不是某整数的平方，所以也算sufficient....这么想错了吗？
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发表于 2009-5-6 18:13:00
