[理工] 离散 3-74

楼主: ok8752665 (dd8752665)   2019-08-05 11:29:14
http://i.imgur.com/bfVguTl.jpg
http://i.imgur.com/8rn0QpK.jpg
请问答案分母的2!是怎么来的
作者: Ricestone (麦饭石)   2019-08-05 13:29:00
就是P(6,4),或者你要说C(6,4)*4!也可
楼主: ok8752665 (dd8752665)   2019-08-05 14:29:00
喔喔 懂了 感恩

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