Which sequence displays exponential behavior?

1). 5, 25, 125, 625 ...

2). 15, 18, 21, 24..

3). 3, 6, 9, 12 ...

4). 4, 16, 32, 64...

1) is the only geometric sequence.

Geometric sequence is a sequence that has exponential behavior.

Step-by-step explanation:

You are looking for a common ratio.

That is you are trying to see which one produces the same number no matter what term you choose divided by it's previous term.

1) So we want to see if the following holds true. If it does, then it is geometric (has exponential behavior).

Simplify:

So one looks good.

2)

Reduce:

These are obviously not the same number. Therefore, this is not geometric.

3)

The only integer is 6/3 which is 2 and the other two aren't so we don't have the same number across the board. Therefore, this one is not geometric.

4)

Simplify:

Not the same across the board so this is not geometric either.