Question

soma dos primeiros termo da PG (2,4,8)

Answer 1

q=$\frac{8}{4} =2$

$Sn= \frac{a_1.(q^{n}-1)}{q-1}$
$Sn= \frac{2.(2^{3}-1)}{2-1}$
$Sn= \frac{2.(2^{3}-1)}{2-1} = \frac{2.7}{1}$
$S_{n}=14$