( n! = n(n-1)\cdots 1 ) for positive integer ( n ), and ( 0! = 1 ).
( \dfrac{n!}{(n-r)!} = {}^nP_r ).
Accedmychevron_right11thchevron_rightmathchevron_rightPermutations And Combinationschevron_rightExercise 7.1
( n! = n(n-1)\cdots 1 ) for positive integer ( n ), and ( 0! = 1 ).
( \dfrac{n!}{(n-r)!} = {}^nP_r ).