Question

determine o oitavo termo de um PG na qual a4 =12 e q=2.

Answer 1

A formula de PG é $a_{n}$=$a_{1}$x$q^{n-1}$
$a_{4}$= 12
q= 2
$a_{8}$=?
Aplicando....

$a_{n}$=$a_{1}$x$q^{n-1}$
$a_{4}$=$a_{1}$x$2^{4-1}$
12=$a_{1}$x$2^{3}$
12=$a_{1}$x8
$\frac{12}{8}$=$a_{1}$
1,5=$a_{1}$

$a_{8}$=1,5x$2^{8-1}$
$a_{8}$=1,5x$2^{7}$
$a_{8}$=1,5x128
$a_{8}$=1024