Question

Факториал
$frac{9!}{10!-9!}$

Answer 1

$frac{9!}{10!-9!}= frac{9!}{1*2*3*4*5*6*7*8*9*10-1*2*3*4*5*6*7*8*9} = frac{1*2*3*4*5*6*7*8*9}{1*2*3*4*5*6*7*8*9*(10-1)}$
$= frac{1}{9}$