mei_5166 发表于 2007-3-18 10:15:06

oG上一道数学题

题目:  If n is a positive integer and n2 is divisible by 72, then the largest positive integer that must divide n is
选项： (A) 6     
          (B) 12
          (C) 24
          (D) 36
          (E) 48


答案是B。看了题解还是不明白。

请大侠们指教！
谢谢～

mei_5166 发表于 2007-3-18 10:18:27

补充

n2是 n的平方

ngkk 发表于 2007-3-18 15:24:12

Given that 72k = n^2
we must find x such that n|x and n must be the largest one
Since 72 = 2*2*3*3*2
Therefore, we let k = 2, then n = 12, then x = 12 so that it can satisified the largest.
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