Multiply: (x+y)2−2xy(x + y)^2 - 2xy(x+y)2−2xy.
x2+y2x^2 + y^2x2+y2
x2−y2x^2 - y^2x2−y2
x2+2xy+y2−2xyx^2 + 2xy + y^2 - 2xyx2+2xy+y2−2xy
(x−y)2(x-y)^2(x−y)2