Question

Temos a PG (3, 6, ...), se Sn = 765, determine n​

Answer 1

Resposta:

n = 8

Explicação passo a passo:

q = 6:3 = 2

$\frac{a_1(q^n-1)}{q-1}=S_n\\\\\frac{3(2^n-1)}{2-1} =765\\\\3(2^n-1)=765:3\\\\2^n-1=255\\\\2^n=255+1\\\\2^n=256\\\\2^n=2^8\\\\n=8$