(x - y)*(x + y) + x + y
1*(x + y)*(x + 1 - y)
(1*(x + y))*(x + (1 - y))
x + y + (x + y)*(x - y)
(x + y)*(1 + x - y)
2 2 x + y + x - y
x + y + x^2 - y^2