Răspuns :
[tex]C20L10 / C20L9 = \frac{ \frac{20!}{10! * (20-10!)} }{ \frac{20!}{9! * (20!-9!)} }
[/tex]
[tex] =\frac{9! * 11!}{10!*10!} = \frac{9!*10!*11}{9!*10*10!} = \frac{11}{10} [/tex]
[tex] =\frac{9! * 11!}{10!*10!} = \frac{9!*10!*11}{9!*10*10!} = \frac{11}{10} [/tex]