We first factor the numerator (top) then cancel.

`(x^2-y^2)/(y-x)` `=((x+y)(x-y))/(-(x-y))` `=(x+y)/-1` `=-x-y`

On the first line of the solution, I am changing the order of the (*y* − *x*) into (*x* − *y*) by placing a minus in front.

This is because

−(*x* − *y*)

= −

x− (−y)= −

x+y=

y−x