Darlene wrote this proof of the identity (x + y)2-(x - y)2 - 4xy Which of the following is a justification for Step 5 of her proof?
Step 1: (x + y)2-(x y)2 = (x+y)(x + y) - (x-7)(x - y)
Step 2: (x+y)(x+y) - (x-7)(x - y) = (P+ xy + xy + y2)-(2-xy- xy + y)
Step 3: (2+xy+ xy + y)-(R- xy- xy+ y) = (x + 2xy + y)-(- 2xy + y)
Step 4: (x2+2x+y)(142-2xy + y) = x + 2xy+y2-+2xy-y?
Step 5 x + 2xy + y2-x2 + 2xy - y2 = 4xy