Question

Calcular a soma dos termos da PG (2,6,...,486)

Answer 1

a1 = 2
a2 = 6
q = 6/2 = 3 *****
an = 486

an = a1 * qⁿ⁻¹
486 = 2 * 3ⁿ⁻¹
3ⁿ⁻¹ 486/2 = 243
3ⁿ⁻¹  = 3⁵
n - 1 = 5
n = 6 *******
S6 = a1 ( 3⁶  - 1)/ ( 3 - 1)
S6 = 2 ( 729 - 1)/2
s6 = 2 ( 728)/2
s6 = 1456/2 = 728 ****