Question

Which of the following is the rule for the geometric

sequence 1, 3. 9. 27, ...?
an = 3.39-1
an = 3.31
an = 1.32
an = 1.39-1

Answer 1

`a_(n)` = 1 .
`3^(n-1)`

Explanation:

The n th term rule for a geometric sequence is

`a_(n)` = a
`r^(n-1)`

where a is the first term and r the common ratio

Here a = 1 and r = 3 ÷ 1 = 3 , thus

`a_(n)` = 1 .
`3^(n-1)`