(x + y)*(x - y - 1)
(x + y)*(x - y - 1*1)
1*(x + y)*(x + -1 - y)
(1*(x + y))*(x - (1 - y))
-(x + y)*(1 + y - x)
2 2 x - x - y - y
x^2 - x - y - y^2
(x + y)*(-1.0 + x - y)