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