来自单乐生的问题
C(4,2)4是下标,2是上标,那用排列组合该得多少?怎么算的?
C(4,2)4是下标,2是上标,那用排列组合该得多少?怎么算的?
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2020-02-01 00:34
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陈丽娟
(4X3)/(2X1)=6C表示组合,下标是n就用n乘(n-1)(n-2)(n-3)...需要乘多少个呢?看上标,上标是2,所以一共需要2个数相乘,即n(n-1),所以得来了4X3.举个例子：C(6,3),上标是3,就用下标6开始连乘3个数6X5X4.算到这步完成了...
2020-02-01 00:37:18
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