Page 65 - Fixtures

@ @pbjïØ Üa@ @UP

n ! = n ×(n − 1)! = n ×(n − 1)×(n − 2)! =

.0! = 1 .1! = 1× 0! n =1

. 6!+ 5!− 4! ()

4!

. 6 !+ 5 !− 4 ! = 6 × 5 × 4 !+ 5 × 4 !− 4 ! = 4 !(30 + 5 − 1) = 34
4! 4! 4!

(n + 2)!+ (n + 1)! ()
n +3

(n + 2)!+ (n + 1)! = (n + 1)!(n + 2 + 1)
n +3 n+3

= (n + 1)!(n + 3) = (n + 1)!
n+3

BAC [Permutations]

. .
.C B A

. ABC , ACB , BAC , BCA , CAB , CBA

{A, B,C }

AB , BA , CA , AC , BC , CB

r ≤n P(n, r ) n S
S r
. Prn n P r