Question

calcule: (10-n)!=10×n!

Answer 1

(10-n)!=10×n!

10-n=10n
10n+n=10
11n=10
n=10/11

Prova
(10-n)!=10×n!
(10- 10/11)! = 10*(10/11)!
(100/11)! = (100/11)!

Espero que tenha entendido!

Exemplo:
(9-n)! = 2*n!

Resposta n=3, pois:

(9-3)! = 2*3!
6!=6!