Question

Dê a soma dos termos desta PG (5,15,45,...,3645).onde há 7 termos

Answer 1

Q = a₂/a₁
Q = 15/5
Q = 3

$S_{n} = \frac{a_{1} . (q^n -1) }{q -1}$
s7 = 5 . (3⁷ -1)/3 -1
s7 = 5 . 2180/2
s7 = 5450