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往事尘

金虫 (小有名气)

[求助] 问题啊!如何证明A为无限集的充要条件是存在A的真子集B且A与B构成对射

问题啊!如何证明集合A为无限集的充要条件是存在A的真子集B且A与B构成双射

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[ Last edited by 往事尘 on 2013-9-11 at 17:31 ]
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Pchief

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2楼2013-09-11 21:03:46
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往事尘

金虫 (小有名气)

引用回帖:
2楼: Originally posted by Pchief at 2013-09-11 21:03:46

请用应助贴我好给你金币

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3楼2013-09-11 22:00:47
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jabile

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引用回帖:
2楼: Originally posted by Pchief at 2013-09-11 21:03:46

A不一定是可数的
应该先从A中选出可数无穷子集,然后再这么做
4楼2013-09-12 08:45:26
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Pchief

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引用回帖:
3楼: Originally posted by 往事尘 at 2013-09-11 22:00:47
请用应助贴我好给你金币
...

我知道确定应助才能得金币,但我决定不要这贴的金币,如果问题已经获得解决,你可以向版主申请退还悬赏金币。
5楼2013-09-12 09:58:53
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wshaoxin

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Pchief 不差钱儿,值得一赞!!
Godhelpsthosewhohelpthemselves!
6楼2013-09-12 12:21:00
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