标题:
求PREP难题~~~!!!
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作者:
duluxstar
时间:
2009-1-5 07:33
标题:
求PREP难题~~~!!!
问: n, y are both positive integers, if 450y=n^3, which of the following must be an integer?
I. Y/3x2^2x5
II. Y/3^2x2x5
III. Y/3x2x5^2
A. None
B. I only
C. II only
D III only
E. I, II, and III
Answer: B.
怎样才能比较快地solve这道题呢? 谢谢指点!!!
作者:
智者多能
时间:
2009-1-5 19:44
450=5^2x3^2x2, 如果450y=n^3,那么Y至少要满足以y=5x3x2^2, 这样才能满足原来等式
作者:
duluxstar
时间:
2009-1-9 20:43
many thanks .
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