Question

Assinale a alternativa que representa corretamente o valor de n, em que 2n! / n!+(n+2)! = 2/7

Answer 1

2n! / [n!+(n+2)!] = 2/7

2n! / [n!+(n+2)(n+1)n!] = 2/7

1/ [1+(n+2)(n+1)] = 1/7

7=1+(n+2)(n+1)

(n+2)(n+1) -6=0

n²+n+2n+2-6=0

n²+3n-4=0

n'=[-3+√(9+16)]/2=(-3+5)/2=1  é a resposta
n'' <0, ñ existe fatorial negativo