Question

determine a soma dos 5 primeiros termos da pg (1,3,9,27)

Answer 1

Sn = [2a1+(n-1).r].n/2

S5 = [2.1+(5-1).3].5/2
S5 = [2+4.3].5/2
S5 = 14.5/2
S5 = 70/2
S5 = 35