Question

The 4th and 5th terms of a GP are 1/27 and 1/729
respectively. Find the sum of n terms of GP​

Answer 1

Answer:

3^9(1- 3^-3n)/26

Step-by-step explanation:

nth term of a gp= a{r^(n-1)}

4th term= ar^3= 1/27

5th term= ar^4= 1/729

4th term/ 5th term= 1/r = 27

so, r= 1/3^3

a=3^6

sum= 3^6 {1-  (3^ -3 )^n}/ { 1-3^-3}

= 3^9(1- 3^-3n)/26