1. Can the numbers in an arithmetic sequence go down?

Yes, if the common difference is negative the terms will decrease.

2. Do you HAVE to take the first term away from the second term to find the common difference?

No, this will work, but you can subtract ANY term from the one after it to find the common difference.

3. How are arithmetic sequences used in real life?

Anywhere there is a pattern there is probably a sequence of some sort.

e.g. Laying tiles or paving stones or depositing a fixed amount of money each week into a bank account could form arithmetic sequences.

4. How do you know which formula to use when finding the sum of terms of an arithmetic sequence?

It depends on the wording of the problem:

If you are not given the last term of the sequence use the longer formula, .

If you are given the last term use,