11!= 1•2•3•4•5•6•7•8•9•10•
11
9!= 1•2•3•4•5•6•7•8•9

11!
___= 10•11=110

9!


( n-1)!= 1 •2•3•.....•( n-1)

(n+3)!= 1•2•3•.....(n-1)•n•(n+1)•(n+2)•(n+3)

После сокращения

1
_________________
n(n+1)(n+2)(n+3)