[中學] 排列組合的難題
http://imgur.com/a/Wdh1u
簡單的異物n中取k問題。
想請問裡面的 (甲乙同時被選上)
到底是怎麼算的..................... 微積分輕鬆掃
排列組合這題看1小時想不懂 =_=
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推
12/21 20:48, , 1F
12/21 20:48, 1F
→
12/21 20:48, , 2F
12/21 20:48, 2F
→
12/21 20:49, , 3F
12/21 20:49, 3F
→
12/21 20:49, , 4F
12/21 20:49, 4F
→
12/21 20:50, , 5F
12/21 20:50, 5F
→
12/21 20:51, , 6F
12/21 20:51, 6F
→
12/21 20:52, , 7F
12/21 20:52, 7F
→
12/21 20:53, , 8F
12/21 20:53, 8F
→
12/21 20:55, , 9F
12/21 20:55, 9F
→
01/09 15:25, , 10F
01/09 15:25, 10F
→
01/09 17:44, , 11F
01/09 17:44, 11F
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01/09 18:43, , 12F
01/09 18:43, 12F
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01/09 18:44, , 13F
01/09 18:44, 13F
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01/09 18:57, , 14F
01/09 18:57, 14F
→
01/09 18:57, , 15F
01/09 18:57, 15F
→
01/09 19:01, , 16F
01/09 19:01, 16F
推
01/09 19:04, , 17F
01/09 19:04, 17F
→
01/09 19:59, , 18F
01/09 19:59, 18F
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01/09 20:04, , 19F
01/09 20:04, 19F
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01/09 20:44, , 20F
01/09 20:44, 20F
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01/09 21:08, , 21F
01/09 21:08, 21F
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01/09 21:10, , 22F
01/09 21:10, 22F
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01/09 21:17, , 23F
01/09 21:17, 23F
推
01/09 21:18, , 24F
01/09 21:18, 24F
→
01/09 21:18, , 25F
01/09 21:18, 25F
→
01/09 21:23, , 26F
01/09 21:23, 26F
推
01/09 21:36, , 27F
01/09 21:36, 27F
推
01/09 21:36, , 28F
01/09 21:36, 28F
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01/09 21:37, , 29F
01/09 21:37, 29F
推
01/09 21:40, , 30F
01/09 21:40, 30F
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01/09 21:42, , 31F
01/09 21:42, 31F
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01/09 21:44, , 32F
01/09 21:44, 32F
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01/09 21:47, , 33F
01/09 21:47, 33F
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01/09 21:50, , 34F
01/09 21:50, 34F
推
01/09 21:56, , 35F
01/09 21:56, 35F
推
01/09 22:04, , 36F
01/09 22:04, 36F
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01/09 22:05, , 37F
01/09 22:05, 37F
→
01/09 22:05, , 38F
01/09 22:05, 38F
推
01/09 22:08, , 39F
01/09 22:08, 39F
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01/09 22:15, , 40F
01/09 22:15, 40F
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01/09 22:19, , 41F
01/09 22:19, 41F
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01/09 22:23, , 42F
01/09 22:23, 42F
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01/09 22:23, , 43F
01/09 22:23, 43F
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01/09 22:25, , 44F
01/09 22:25, 44F
推
01/09 22:25, , 45F
01/09 22:25, 45F
推
01/09 22:26, , 46F
01/09 22:26, 46F
→
01/09 22:26, , 47F
01/09 22:26, 47F
推
01/09 22:30, , 48F
01/09 22:30, 48F
推
01/09 22:33, , 49F
01/09 22:33, 49F
推
01/09 22:38, , 50F
01/09 22:38, 50F
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01/09 22:40, , 51F
01/09 22:40, 51F
推
01/09 22:41, , 52F
01/09 22:41, 52F
→
01/09 22:43, , 53F
01/09 22:43, 53F
推
01/09 22:43, , 54F
01/09 22:43, 54F
推
01/09 22:45, , 55F
01/09 22:45, 55F
推
01/09 22:48, , 56F
01/09 22:48, 56F
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01/09 22:51, , 57F
01/09 22:51, 57F
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01/09 23:04, , 58F
01/09 23:04, 58F
→
01/09 23:05, , 59F
01/09 23:05, 59F
推
01/09 23:14, , 60F
01/09 23:14, 60F
→
01/09 23:24, , 61F
01/09 23:24, 61F
→
01/09 23:25, , 62F
01/09 23:25, 62F
→
01/09 23:32, , 63F
01/09 23:32, 63F
推
01/09 23:35, , 64F
01/09 23:35, 64F
推
01/10 00:28, , 65F
01/10 00:28, 65F
推
01/10 00:30, , 66F
01/10 00:30, 66F
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01/10 00:30, , 67F
01/10 00:30, 67F
→
01/10 00:31, , 68F
01/10 00:31, 68F
推
01/10 00:49, , 69F
01/10 00:49, 69F
推
01/10 01:02, , 70F
01/10 01:02, 70F
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01/10 01:20, , 71F
01/10 01:20, 71F
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01/10 01:23, , 72F
01/10 01:23, 72F
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01/10 01:41, , 73F
01/10 01:41, 73F
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01/10 01:47, , 74F
01/10 01:47, 74F
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01/10 02:13, , 75F
01/10 02:13, 75F
推
01/10 02:15, , 76F
01/10 02:15, 76F
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01/10 03:09, , 77F
01/10 03:09, 77F
推
01/10 03:11, , 78F
01/10 03:11, 78F
推
01/10 07:07, , 79F
01/10 07:07, 79F
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01/10 08:38, , 80F
01/10 08:38, 80F
推
01/10 10:22, , 81F
01/10 10:22, 81F
推
01/10 13:38, , 82F
01/10 13:38, 82F
推
01/10 14:23, , 83F
01/10 14:23, 83F
推
01/10 15:34, , 84F
01/10 15:34, 84F
推
01/10 15:35, , 85F
01/10 15:35, 85F
推
01/10 16:20, , 86F
01/10 16:20, 86F
推
01/10 17:48, , 87F
01/10 17:48, 87F
→
01/10 21:14, , 88F
01/10 21:14, 88F
推
01/11 01:41, , 89F
01/11 01:41, 89F
推
03/14 15:33, , 90F
03/14 15:33, 90F
推
05/23 18:24, , 91F
05/23 18:24, 91F