Question

Номер 329 пожалуйста!!!!!!!

Answer 1

a)
$C^{n+1}_{2n}:C^{n-1}_{2n+1}= frac{(2n)!}{(n+1)!cdot (2n-n-1)!}cdot frac{(n-1)!cdot (2n+1-n+1)!}{(2n+1)!}= frac{n+2}{2n}. \ \ frac{n+2}{2n}= frac{7}{13} \ \ 13(n+2)=2ncdot 7 \ \ n=26$

б)
$C^{n}_{2n-1}:C^{n-1}_{2n}= frac{(2n-1)!}{n!cdot (2n-1-n)!}cdot frac{(n-1)!cdot (2n-n+1)!}{(2n)!}= frac{n+1}{2n}. \ \ frac{n+1}{2n}= frac{9}{17} \ \ 17(n+1)=2ncdot 9 \ \ n=17$