Why do you think adding and subtracting polynomial expressions is like adding and subtracting expressions?

Polynomials are closed under addition and subtraction, which is fancy mathspeak that means that whenever we add or subtract two polynomials, we always get another polynomial. In that way, they behave a lot like the numbers you're probably already familiar with. Adding and subtracting:

And it works the same with polynomials!

is there any photos or whatever?