Question

considere a pg (3,12,...)se somarmos os n primeiros termos dessa pg, encontraremos 4095. Determine n

Answer 1

Sn=(a1*(q^n-1))/(q-1) ⇒ 4095=(3(4^n-1))/(4-1) ⇒ 4095=(3(4^n-1))/3 ⇒ 4095=4^n-1 ⇒ 4^n=4096 ⇒ 4^n=4^6 ∴ n=6