Question

For a gp 5,15,45,135,....Sn=

Answer 1

Answer:

common ratio = 3

1st term = 5

so Sn =

$\frac{a( {r}^{n} - 1)}{r - 1} = \frac{5( {3}^{n} - 1)}{3 - 1} = \frac{5}{2} ( {3}^{n} - 1)$