1. X is a positive integer. 2-height of X is defined as the greatest negative integer n where 2^n is a factor of X. K and M are two positive integers. Whether 2-height of K is greater than 2-height of M?
a. K is greater than M
b. K is even times of M
(Key: B)
(by rosemsem)
题义解析：说对于含2的n次方的数, 2-height 指的是n的值。问k和m谁的2-height大？
(1) K>M
(2) K除以M是偶数.
(please notice K,k; M,m; e)
K = a* 2^k;
M = b* 2^m;
(1) k>m, means nothing.
(2) k/m= (a/b) * (2^k/2^m) = 2^e;
A, b must be odd number, or you can extract at least one more 2, which gonna change k or m. So in this case, (a/b) must be 1, otherwise it would be a fraction.
In a word, k-m=e. K>m.
B is sufficient.
我觉得是不是选E呢
设
k=26＊5 m＝5，则k/m为偶，符合条件B。 2－height K＝6 所以 2－height K>m
23＊5 m=5 , 则k/m为偶，符合条件B。 2－height K＝3 所以 2－height K<m
所以我觉得 2－height k 和m的大小没法确定啊。
大家看看我设的这两个数有没有问题。 | 
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发表于 2011-3-19 07:09:07
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