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标题: 问道数学题! [打印本页]

作者: XIAOXIANGXI    时间: 2006-5-21 06:36     标题: 问道数学题!

If the sequence x1, x2, x3, …, xn, … is such that x1 = 3 and xn+1
= 2xn – 1 for n ≥ 1, then x20 x19 =

For a certain race, 3 teams were allowed to enter 3 members each. A team earned 6 – n points whenever one of its members finished in nth place, where 1 ≤ n ≤ 5. There were no ties, disqualifications, or withdrawals. If no team earned more than 6 points, what is the least possible score a team could have earned?


A. 0

B. 1

C. 2

D. 3

E. 4

还请赐教。

另外机考数学的难度跟GWD有多大差异啊?

Thanks


作者: daoying    时间: 2006-5-21 16:00

可以推出

x1=1+2^1

x2=1+2^2

x3=1+2^3

........

x19=1+2^19

x20=1+2^20

所以x20-x19 = 2^20-2^19=2^19






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