It may help you to read Introduction to Algebra first
"Like terms" are terms whose variables (and their exponents such as the 2 in x2) are the same.
In other words, terms that are "like" each other.
Note: the coefficients (the numbers you multiply by, such as "5" in 5x) can be different.
Are all like terms because the variables are all x
Are all like terms because the variables are all xy2
If they are not like terms, they are called "Unlike Terms":
|Unlike Terms||Why they are "Unlike Terms"|
|-3xy||-3y||12y2||← these are all unlike terms
(xy, y and y2 are all different)
Combining Like Terms
You can add like terms together to make one term:
Example: 7x + x
They are both like terms, so you can just add them:
7x + x = 8x
Example: 3x2 - 7 + 4x3 - x2 + 2
Some of the terms are like terms.
Combine like terms:
(3x2 - x2) + (4x3) + (2 - 7)
Then add like terms:
2x2 + 4x3 - 5