Question

determine a soma dos 6 ( seis) primeiros termos da P.G. ( 2,6,18,..)
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Answer 1

R: 728

q = a2/a1 = 6/2 = 3

a1 = 2

sn = a1 × (q^n -1)/q - 1

s6 = 2 × (3⁶ - 1)/3 - 1

s6 = 2 × 728/2

s6 = 1456/2

s6 = 728

Answer 2

Resposta

$\boxed{S_{6}=128}$

Explicação passo-a-passo:

$a_{n}=\frac{a_{1}.(q^n-1)}{q-1} \\\\q=\frac{6}{2}\\\\q~=3\\\\S_{6}=\frac{2.(3^6-1)}{3-1}\\\\S_{6}=\frac{\diagup\!\!\!\!2.(3^6-1)}{\diagup\!\!\!\!2} \\\\S_{6}=3^6-1\\\\S_{6}=129-1\\\\S_{6}=128$