Question

Find the sum of 20terms of the series 2 +6+18

Answer 1

Answer:

2 +6+18+54+......

this series is GP.

n=20

r=6/2=3

Sn=a(rⁿ -1) /(r-1)

S20= 2(3^20 -1) /(3-1) =3^20 -1