Question

determine n

n!+2(n-1)!/(n-2)! = 18

​

Answer 1

Olá!

n(n-1)(n-2)!+2(n-1)(n-2)!/(n-2)!=18
(n-2)![n(n-1)+2(n-1)]/(n-2)!=18
n(n-1)+2(n-1)=18
n²-n+2n-2=18
n²+n-20=0

Δ=b²-4ac
Δ=1²-4.1.(-20)
Δ=1+80
Δ=81

n’=-b+√81/2a
n’=-1+9/2.1
n’=8/2
n’=4

n”=-b-√81/2a
n”=-1-9/2.1
n”=-10/2
n”=-5

Espero ter ajudado!