Question

Calcule a soma dos termos da pg finita 8,24,...,472392

Answer 1

Olá Ester 

PG

u1 = 8
u2 = 24

razão
q = u2/u1 = 24/8 = 3

termo geral
un = u1*q^(n - 1)

8*3^(n - 1) = 472392
3^(n - 1) = 472392/8 = 59049 

3^(n - 1) = 3^10
n = 11

soma
Sn = u1*(q^n - 1)/(q - 1)

S11 = 8*(3^11 - 1)/(3 - 1)
S11 = 4*(177147 - 1) = 708584

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