Question

Calcule a soma dos 5 primeiros termos da PG (2,8,...).

Answer 1

q = a₂ / a₁
q = 8 / 2
q = 4

a₅ = a₁ * q⁴
a₅ = 2 * 4⁴
a₅ = 2 * 256
a₅ = 512

Sn = a₁ * (qⁿ - 1) / q - 1
S₅  = 2 * (4⁵ - 1) / 4 - 1
S₅ = 2 * (1024 - 1) / 3
S₅ = 2 * 1023 / 3
S₅ = 2 * 341
S₅ = 682