Question

Dada a PG (3,9,27,81...) determine o 20º termo.

Answer 1

$PG~~ (3,9,27,81...)\\\\\\ a_1=3\\ q\to~9:3=3\\n=20\\ a_n=a_{20}=?\\\\\\ a_n=a_1\times q^{n-1}\\\\\\ a_{20}=3\times 3^{20-1}\to\\\\ a_{20}=3\times 3^{19}\to\\\\ a_{20}=3\times 1.162.261.467\to\\\\ \large\boxed{a_{20}=3.486.784.401}$