å
çä»A, Bä¸å¯ä»¥éåºå¤å°ç»ä¸åç5个æ°
å°±æ¯ä»{1, 2, ..., 9}ä¸éåº5个æ°ï¼å¯ä»¥éåºC(9, 5)ç»ã
å»æä¸æ»¡è¶³æ¡ä»¶çéæ³æéåºçã
ä¸æ»¡è¶³æ¡ä»¶çéæ³æ两ç§ä¸åçæ
åµï¼
åç±»1ï¼5个æ°é½æ¯ä»{1, 2, 3, 4, 5}ä¸éåºæ¥ç
è¿æ ·çæC(5, 5)ç»ã
åç±»2ï¼5个æ°æ4个æ¯ä»{1, 2, ,3, 4, 5}ä¸éåºæ¥çï¼1个æ¯ä»{6, 7, 8, 9}ä¸éåºæ¥ç
è¿æ ·çæC(5, 4)C(4, 1)ç»ã
å æ¤ï¼æè¦æ±éåºä¸åç5个æ°ï¼æ°å¥½æC(9, 5) - C(5, 5) - C(5, 4)C(4, 1)ç»ã
é£ä¹ï¼å¾å°ç5ä½æ°ç个æ°å°±æ¯æéåºæ¥ç5个æ°è¿è¡å
¨æåçæåæ°ã
(C(9, 5) - C(5, 5) - C(5, 4)C(4, 1))P(5, 5)
= 12600.
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