Question

calcule a soma dos 13 primeiros termos da P.G(02,06,18...)

Answer 1

6/2=  3 logo q=3

entao façamos:

 

$<var>S_n=\frac{a_1(q^n-1)}{q-1}\\S_1_3=\frac{2(3^1^3-1)}{3-1}\\S_1_3=\frac{2(1594323-1)}{2}\\S_1_3=\frac{2*1594322}{2}\\S_1_3=\frac{3188644}{2}\\\\S_1_3=1594322</var>$

Answer 2

Lucida,

 

Numa PG:

Sn = a1(q^n - 1) / (q - 1)

 

Do enunciado:

q = 18/6 = 6/2 = 3

a1 = 02

  n = 13

 

S13 = 02(3^13 - 1) / (3 - 1)

        = 02(1594323 - 1) / (2)

        = 02(1594322) / 2

        = 1594322

 

S13 = 1594322