If x+y=r and x-y=s, in terms of x and y, what is r^2-s^2? Please show step by step. Thanks.

Let’s do this two ways. First, with substitution. If and , then we can rewrite as . Then we can simplify that:

The other way to go is to plug in. Say and . That makes and . Now you’re looking for . Which answer choice gives you 24 when you plug in and ? does: .