作者Honor1984 (奈何上天造化弄人？)
看板Math
标题Re: [中学] 国二题目
时间Wed Jan 8 21:49:09 2020
※ 引述《maggie531 (一起走吧~)》之铭言：
: 请教各位大神，这三题该如何解
: 感谢各位帮忙
:
: https://i.imgur.com/Oj4WhDL.jpg
1.
m正整数 > (a - 1)
a^2 - a + 3 = (a - 1)m
=> (a - 1)(m - a) = 3
a - 1 = 1(不合)
a - 1 = 3 => a = 4, m = a + 1 = 5
2.
N - [N] = [N] - (N - [N]) = 2[N] - N
=> 2N = 3[N]
0 <= 2[N] - N = N - [N] < 1
=> 0 <= [N] < 2
[N] = 0 = N(不合)
[N] = 1 => N = 3/2
3.
开头为n的会结束於n + n + 3 - 1 = 2n + 2
2n + 2 = 2018
=> n = 1008
开头为1008 ~ 2018的人都会叫到2018
共n + 3 = 1011人
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