Write a rule for the nth term of the geometric term given the two terms a_1=1,a_3=9

Aarav Atkins

Aarav Atkins

Answered question

2022-10-13

Write a rule for the nth term of the geometric term given the two terms a 1 = 1 , a 3 = 9

Answer & Explanation

Milton Hampton

Milton Hampton

Beginner2022-10-14Added 16 answers

The general formula for a term of a geometric sequence is:
a n = a r n - 1
where a is the initial term and r the common ratio.
In our example, we find:
9 = a 3 a 1 = a r 2 a = r 2
Hence r = ± 3 , giving two possible sequences.
The rule for the nth term of this sequence can be written:
a n = 3 n - 1
or:
a n = ( - 3 ) n - 1

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?