Re: [理工] [離散] 98台大電機

看板Grad-ProbAsk作者mqazz1 (無法顯示)時間14年前 (2011/08/01 10:48)推噓9(9推 0噓 8→)

留言17則, 7人參與討論串2/5 (看更多)

※ 引述《ceo890710 (Drinking)》之銘言： : Let's define set S by 3(屬於)S ; a+b(屬於)S if a(屬於)S and b(屬於)S 我想這應該只是單純的類推而已先仔細看它的題目 3屬於S a+b屬於S if a屬於S and b屬於S 已經知道3屬於S 先令 a=3屬於S, b=3屬於S => a+b=6屬於S => 3跟6都屬於S 一直推下去3+6, 3+3+6, 3+3+3+6, ...都屬於S : Which of the following statements is true? : (a) S is a empty set 題目一開始就說3屬於S : (b) S is the set of integers that are not divisible by 3 3的倍數 : (c) S is the set of positive integers divisible by 3 : (d) S is the set of all positive integers 1, 2, 4, 5, 7,...不屬於S : (e) None of the above : 我看解答給的答案是C，想說只有那三個條件怎麼能確定都是3的倍數呢 : --------------------------------------------------------------------- : One hundred students enter a locker room that contains 100 lockers. : The first student open all the lockers.The second student changes the : status(from open to closed, and vice versa) of every other locker, : starting with the second locker.The third student then changes the : status of every third locker,starting with the third locker.In general, : for 1<=K<=100,the kth student changes the status of every kth locker, : starting with the kth locker.After the 100th student has gone through : the lockers,which lockers are left open? : 想問一下這題大家會怎麼解? 待高手@@ -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 140.118.110.186

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ceo890710

08/01 10:51, , 1^F

08/01 10:51, 1^F

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lexa

08/01 11:25, , 2^F

08/01 11:25, 2^F

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lmr3796

08/01 12:14, , 3^F

08/01 12:14, 3^F