I'm lost can you tell me how to do this step by step

You haven't said what you need to "do" with it. I'm going to take a wild guess that you've been asked to 'factor' it. I don't have any step-by-step method for realizing that, and then doing it. But if you've done all the homework on multiplying twobinomials, and kind of almost understood it, then you might recognize this expression as the result AFTER two binomials got multiplied. Factoring it means to un-multiply it, and get the original two binomials. This is the product of (a-x) times (a+y).

Hello! mark me brainliest
answer:
congruent segments
step-by-step explanation:
congruent segments. take a line, cut it in half, superipose one half over the other half; you'll have congruence.