How do you factor monomials?

All you do is write the prime factorization. I'll do an example:

50y

First, you find the prime factorization of the coefficent using a factor tree, but it won't let me do that, so this is what the prime factorization should look like:

2x5x5

Then you add the variable:

2x5x5xy

When you have a negative coefficent, just put a negative one in front of your answer.

-50y = -1x2x5x5xy