Whats 1-(x+y)2?

Question

that 2 at the end is squared

factor it completely

Answer 1

Let x+y = z
1 - z^2 =
(1+z)(1-z)

So
1 - (x+y)^2 =
(1 - (x+y))(1 +(x+y))
(1- x - y)(1 +x +y)