Question

Determine o 20 termo da pg(1,3,9,27....

Answer 1

Vamos começar determinando a razão da PG:

$razao\,(q)~=~\frac{a_2}{a_1}\\\\\\razao\,(q)~=~\frac{3}{1}\\\\\\\boxed{razao\,(q)~=~3}$

Utilizando a equação do termo geral da PG, temos:

$\boxed{a_n~=~a_1~.~q^{n-1}}\\\\\\\\a_{20}~=~a_1~.~3^{20-1}\\\\\\a_{20}~=~1~.~3^{19}\\\\\\\boxed{a_{20}~=~3^{19}}$