Question

calcule a soma dos 6 primeiros termos da P.g ( 320,160,80 ...)

Answer 1

q = a₂ / a₁

q = 160/320

q = 1/2

a₆ = a₁ * q⁵

a₆ = 320 * (1/2)⁵

a₆ = 320 * 1/32

a₆ = 320/32

a₆ = 10

S₆ = a₁ * (qⁿ - 1) / q - 1

S₆ = 320 * [ (1/2)⁶ - 1 ] / 1/2 - 1

S₆ = 320 * [ 1/64 - 1 ] / - 1/2

S₆ = 320 * [ - 63/64 ] / - 1/2

S₆ = - 20 160/64  /  - 1/2

S₆ = - 20 160/64  *  - 2/1

S₆ = 20 160 / 32

S₆ = 630