Question

calcule a soma dos 20 primeiros termos da pg(2,6,18...)

Answer 1

a1 = 2
q = 6 ÷ 2 = 3

$S20 = \frac{a1(q^n -1)}{q-1} \\ \\ S20 = \frac{2(3^{20}-1)}{3-1} \\ \\ S20 = \frac{2 * 3486784400}{2} \\ \\ S20 = 348784400$