Question

determine a soma dos 10 primeiros termos da PG (1,3,9,27)

Answer 1

q = a2 / a1
q = 3 / 1
q = 3

Sn = a1 * (q^n - 1) / q-1
S10 = 1 * (3^10 - 1) / 3 - 1
S10 = 1 * ( 59049 - 1) / 2
S10 = 59048 / 2
S10 = 29 524

Answer 2

$\boxed{Sn= a1* \frac{(q ^{n-1} )}{q-1} }$

S10= 1*(3^10-1)/3-1
S10 = 1*(59049-1)/2
S10 = 59048/2
S10= 29524

Beleza?