How does this get reduced to simplest form?

Question

x2 – y2 divided by y - x

Answer 1

-(x+y) or -x-y

(-y-x)(y-x) = x^2 - y^2

Answer 2

factorise numerator to (x + y)(x - y)

this is divided by (-x+y) or -(x - y)

bring minus out the front cancell off the denominator with the same term in the numerator and you are left with -(x + y) or -x - y