Combine like terms:

4a + 3 – + 9a – + 1

The first two like terms are 4a and 9a because they both have the same variables. To combine them, we simply add them together.

4a + 9a = 13a

The second set of like terms are 3 and 1. They are alike because they both do not have any variables. To combine these two together we add them as well.

3 + 1 = 4

The final set of like terms is   and . To combine them, we have to subtract.

– =

The final equation, after we have combined all the like terms, is…

13a + 4