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标题: 请教ppt 一道数学题 [打印本页]

作者: jessieyang81 时间: 2006-10-21 21:36
标题: 请教ppt 一道数学题

For every positive even integer n, the function h(n) is defined to be the productive of all the even integers from 2 to n,inclusive.If p is the smallest prime factor of h(100)+1, then p is

(1) between 2 and 10

(2) between 10 and 20

(3) between 20 and 30

(4) between 30 and 40

(5) greater than 40

作者: wangrui523 时间: 2006-10-21 22:26

是(5)吗?

h(100)+1=2X4X6X8X......X98X100+1=1X2X3X.....X49X50X(2的50次方)+1

则h(100)+1除以任何小于50的数都会余1,也就是h(100)+1不会被任何小于50的数整除,当然也包括任何小于40的质数.

因此最小的质因子肯定是大于40的

作者: jessieyang81 时间: 2006-10-21 23:11

答案就是(5).

终于明白了,多谢.

作者: wangrui523 时间: 2006-10-21 23:29

You are welcome

我是考前两周,今天正式开始复习MATH,想多做点难题,有问题问我哈

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