Question

Determine whether the sequence below is a geometric sequence and, if so, find a formula that describes the sequence.

1, 3, 9, 27, 81, …

Answer 1

Umm...
3/1=3
9/3=3
27/9=3
81/27=3
...
Is it a geometric sequence?

Answer 2

Yes

Answer 3

right?

Answer 4

Yes, now you have to find the rule.

Answer 5

knowing that the common ratio is 3.

Answer 6

an= 3^n-1?

Answer 7

It came out as 9.

Answer 8

So its not that one.

Answer 9

I dont think it is an= 3^n

Answer 10

I think you had it, but the parentheses were messed up,
Would you like to try again with
\[a_n = 3^{n-1}\]

Answer 11

an=3(1^n-1)
?

Answer 12

oh ok.

Answer 13

Good job!

Answer 14

Thats it?

Answer 15

Yep. You've got everything the question asked for.
It's seems simpler than you thought, right?

Answer 16

Yep. There is one more thats sorta like it that i dont get

Answer 17

1, 2, 3, 4, 5, ...

Answer 18

Since it is a geometric sequence, i have to multiply.

Answer 19

Is it a geometric sequence?

Answer 20

Or is it an arithmetic sequence?

Answer 21

Yes.

Answer 22

Geometric

Answer 23

Does 2/1=3/2=4/3=5/4...
If not it is not a geometric sequence.

Answer 24

an=2*(1)^n-1 work for it?

Answer 25

Oh wait, it might not be a geometric sequence at all.

Answer 26

no, it is not.
It is an arithmetic sequence.

Answer 27

Oh ok, thanks.

Answer 28

Welcome! :)