$\definecolor{red}{RGB}{255,0,0}$$\definecolor{black}{RGB}{0,0,0}$
  1. $A_k^n$
  2. $A_k^n$
  4. $A_k^n$
    • $$\color{blue}{\rightarrow}\color{black}\;A_k^n \;= \;\frac{n!}{(n-k)!}$$
  1. $n$
  2. $n$
  4. $n$
  1. $k$
  2. $k$
  4. $k$
Combinatorics: Permutation (Arrangements) of n objects taken k at a time

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