Question

Which of the sequences is an arithmetic sequence?

Answer 1

A -20, -27, -34, -41,-48

Explanation:

An arithmetic sequence is one that has the same thing added or subtracted each time

A -20, -27, -34, -41,-48

We subtract 7 each time

B 154,71,8,5,2

There is not constant number that we add or subtract

C 1,5,10,15,20

It looks like we add 5, but from the first to second term, we only add 4, so it is not an arithmetic sequence

D 12,-24,36,-48,60

We are multiplying not adding or subtracting so this is geometric

Answer 2

A

Explanation:

Arithmetic sequences are those that have a common difference, as opposed to having a common ratio or no common difference at all.

Look at each answer choice:

A: Find the common difference by taking one term and subtracting the previous term from it.

-27 - (-20) = -27 + 20 = -7

-34 - (-27) = -34 + 27 = -7

If we keep doing this, we'll see that they all have a difference of -7, so this is an arithmetic sequence.

If we inspect the other three answer choices, we'll see that they do not have common differences.

Thus, A is the answer.