Question

#1: Given the geometric sequence 3, 9, 27, 81...

• write the explicit formula. Determine the 20th term of the sequence

Answer 1

The given geometric series is:

3,9,27,81

Explanation:

common ratio: r = (
`a_n +1/ a_n`)

r = 3

20th term of geometric series is that :

`3^(1) =3\\3^2=9\\3^3=27\\3^4=81\\3^5=243\\.\\.\\.\\.\\.\\3^20 = 3486784401`

Answer 2

3486784401

Explanation:

a=3, r = T2/T1 = 9/3=3

Tn = ar^(n-1)

T20 = ar^(20-1)

T20 = ar^19

T20 = 3×(3^19]

T20 = 3486784401