Question

calcule a soma dos 5 primeiros termos da pg (2,6,18,...)

Answer 1

$a_{1} =2$

$q= \frac{6}{2} =3$

$S_{n} = \frac{a_{1}.( q^{n}-1 )}{q-1}$

$S_{5} = \frac{2.( 3^{5}-1 )}{3-1} = \frac{2.( 243-1 )}{2}= 242$