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标题: 数学prep两道题求教，谢谢 [打印本页]

作者: Gooo 时间: 2008-1-5 13:05
标题: 数学prep两道题求教，谢谢

终于重新编辑好了

19. 2463-!-item-!-187;#058&002761

For a finite sequence of nonzero numbers, the number of variations in
            sign is defined as the number of pairs of consecutive terms of the sequence for
            which the product of the two consecutive terms is negative. What is the number of variations in sign for the
            sequence 1, -3, 2, 5, -4, -6 ?

(A) One
(B) Two
(C) Three
(D) Four
(E) Five

7. 905-!-item-!-187;#058&000575

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

(A) between 2 and 10

(B) between 10 and 20

(D) between 30 and 40

(E) greater than 40

[此贴子已经被作者于2008-1-5 13:14:30编辑过]

作者: Gooo 时间: 2008-1-5 13:09
编辑上出了点问题，有乱码，实在编辑不了了，大家包涵。

作者: Gooo 时间: 2008-1-5 13:39
怎么别人的问题都有人讨论，我的没人理。呼唤牛人帮帮忙吧～～～～

作者: LEECA 时间: 2008-1-5 14:30

终于重新编辑好了

19. 2463-!-item-!-187;#058&002761

For a finite sequence of nonzero numbers, the number of variations in
   sign is defined as the number of pairs of consecutive terms of the sequence for
   which the product of the two consecutive terms is negative. What is the number of variations in sign for the
   sequence 1, -3, 2, 5, -4, -6 ?

(A) One
(B) Two
(C) Three
(D) Four
(E) Five

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答案是3吗，如果是的话就是说有几对前后连续的数乘积为负数。

那就是1，-3和-3，2和5，-4

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答案是3吗，如果是的话就是说有几对前后连续的数乘积为负数。

那就是1，-3和-3，2和5，-4

[此贴子已经被作者于2008-1-5 15:17:01编辑过]

作者: jovianne 时间: 2008-1-5 14:44

第一题选c，第二题选e么？

1.问相邻两数乘积为负的数有几对？显然有3对，1×-3，—3×2，5×-4

2，原式=2^50×（1×2×3×……×50）+1

所以h（100）+1除以任何小于50的数都余1

所以p>50

大概是这样吧～

作者: Gooo 时间: 2008-1-5 23:00
谢谢两位高人。第一题答案是C，原题目那句太长，看半天不知道说什么-_-!
第二题答案是E,但是楼上的解释我还得再琢磨琢磨，看不大懂。汗~

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