[理工] 離散-Countable

看板Grad-ProbAsk作者 (thankakimo)時間17年前 (2009/03/19 16:09), 編輯推噓1(1推 0噓 5→)
留言6則, 3人參與, 最新討論串1/1
題目: If A and B are two countable sets,show that A*B is also countable. 問題: 請問各位大大這題要如何解答呢 ?? 煩請指導 感謝 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 163.14.68.41
推
03/19 16:11, , 1F
我只想到 N*N -> N 這樣証 不知道對不對
03/19 16:11, 1F
→
03/19 17:39, , 2F
A -> N, B -> N
03/19 17:39, 2F
→
03/19 17:40, , 3F
A*B -> N -> N -> N
03/19 17:40, 3F
→
03/19 17:40, , 4F
so, A*B is countable
03/19 17:40, 4F
→
03/19 17:40, , 5F
第二行打錯...更正:A*B -> N*N -> N
03/19 17:40, 5F
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03/19 21:10, , 6F
瞭解了 感謝S大和P大解答
03/19 21:10, 6F
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