Question

calcule a soma dos nove primeiros termos da pg 5 15

Answer 1

an = a1.q^n-1


an = ?
a1 = 5
n = 9
q = 3

an = 5.3^9-1
an = 5.3^8
an = 5.6561
an = 32805


Sn = ( an.q - a1)/q - 1

Sn = (32805.3 - 5)/3 - 1
Sn = 98415 - 5/2
Sn = 98410/2
Sn = 49.205