Question

I need help answering this question

Answer 1

If this is an arithmetic sequence, each of the terms will have a common difference. Let's check.

`\begin{gathered} 3-21=-18 \\ 21-147=-126 \end{gathered}`

As we can see, each of the terms does not have a common difference. The first one is -18 while the other one is -126. Therefore, this is not an arithmetic sequence.

Now, let's check if this is a geometric sequence. If it is, each of the terms will have a common ratio.

`\begin{gathered} 3/21=(1)/(7) \\ 21/147=(1)/(7) \end{gathered}`

As we can see, each of the terms has a common ratio which is 1/7. Therefore, 147, 21, 3 is a geometric sequence and the common ratio is equal to 7.