1. probability theory - combination analysis

【README】

This article summarizes from 《 Basic course of probability theory 》 by M.Ross , Wall crack recommendation ;

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【1.3】 array （ Consider the order ）

1） example 3d：

• use 6 Letters PEPPER array , How many different arrangements are there ？
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 2） Reasoning
about n Elements , If one n1 The two elements are the same , other n2 The two elements are the same ,......,nr Elements are the same , Altogether

Two different arrangements ;

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【1.4】 Combine （ Regardless of order ）

1） Combinatorial calculation
Generally speaking , If you consider the order , from n Of the elements r Elements in a group , share

Different ways , And each contains r The groups of elements are recalculated r! Time , therefore , from n Of the elements r The number of different groups is