1 . 设X,Y为任意集合,映射
.定义:对任意
,若
,则
,此时的
为单射.
(1)试在
上给出一个非单射的映射;
(2)证明:
是单射的充分必要条件是:给定任意其他集合
与映射
,若对任意
,有
,则
;
(3)证明:
是单射的充分必要条件是:存在映射
,使对任意
,有
.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/86d7786f55f767e0a301b5032cdacc79.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4645f4c284aef83b9d7edc909ce75168.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/33bd24e647a626899a243a3f3984f90a.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/f27822887caad20f3a075ca2fb74155c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4ff0af96ea467337cb30c4c765b5f7.png)
(1)试在
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ff048206370cd239052751e22f51089e.png)
(2)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4ff0af96ea467337cb30c4c765b5f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/0d8b9ad2fcfff3dd546c5fdbedfe6238.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/47d2e22788e03d6846442ce299b67bd7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/02ab73f0717678abfa9f8addc42be0c7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ce86cc928b228eba243c4bbfae8247ef.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/683ee65c22bb8f6350feef3a3371a95f.png)
(3)证明:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/ca4ff0af96ea467337cb30c4c765b5f7.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/b2216c6b89948de65d2e8488c2071a61.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/4fd9b15b5cdf1c131ebf7cf2776cf7a4.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/5e0ab2f691659dfb9857e81cabc3142e.png)
您最近一年使用:0次
2 . 函数
的解析式为
,值域为
,则符合要求的函数
的个数为( )
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/942c2141d01bde6b48210c56a17fc75e.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/c565889556c2f415ba5c17e1c1ced41c.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/e565001c699e5e221ed616dd7be2bb83.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/09f86f37ec8e15846bd731ab4fcdbacd.png)
A.16个 | B.945个 | C.2025个 | D.1个 |
您最近一年使用:0次
3 . 据历史记载,美日在中途岛(Midway)海战前,美方截获了日方密码电报,据美方已破译的密码得知,日方将向某岛进行军事活动,但关键含有地点的部分却被日方换成了另一种密码.经专家研究,估计是一种密匙密码,且密匙为3位.所谓密匙密码是指:将一段英文字母的明文(未加密前原文)经过对某一组数字(即密匙)的变换,改变成了另一组英文字母成为密文(加密后的文字)例如:明文:
(不计空格,不计大小写)在密匙为:1 9 2的条件下,变换过程如下图所示:
则密文为:
,试根据上面信息回答下面问题:
(1)在密匙为111的条件下,填写下表,并写出密文;
密文____________________.
(2)若![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e15de042ebf4d454a087d9d7245b0b2.png)
请填写下表,并写出密匙;
密匙为_____________.
(3)若下面即是那段包含地点(Midway)的破译不出的密文:
,且此段密文也是3位密匙加密,试填写下表,写出密匙,并将此段密文翻译成明文.(不必证明,写出明文即可)
密匙为___________,明文为_________.
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8e1199c50aa9f4377250cb26bc3724e0.png)
s | t | u | d | e | n | t |
1 | 9 | 2 | 1 | 9 | 2 | 1 |
t | c | w | e | n | p | u |
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/d4ce1ed5abff05c5609344896eac946f.png)
(1)在密匙为111的条件下,填写下表,并写出密文;
s | t | u | d | e | n | t |
(2)若
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/6e15de042ebf4d454a087d9d7245b0b2.png)
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/70ab9a53020088b09879ececa7bee1ad.png)
s | t | u | d | e | n | t |
(3)若下面即是那段包含地点(Midway)的破译不出的密文:
![](https://staticzujuan.xkw.com/quesimg/Upload/formula/8c1be7cf9cfde23043448eabb187e10c.png)
c | w | b | c | f | s | o | l | l | y | d | g |
您最近一年使用:0次