Question

determine o valor de n! . (n+1)!/(n-1).n! =20​

Answer 1

Explicação passo-a-passo:

n! .(n+1)!

______=20

(n-1)! n!

(n+1).n.(n-1)!

_________=20

(n-1)!

(n+1).n = 20

n² + n -20=0

∆= 1² -4.1.(-20)

∆= 1 +80

∆= 81

n= - 1 +√81/2

n= - 1 +9/2

n= 8/2

n=4

S = { 4}