|X+Y+XY|^2=√(Xˆ2+Yˆ2)^2
X^2 +Y^2 +X^2 Y^2 +XY+X^2 Y+XY^2 =X^2 +Y^2
X^2 Y^2 +XY+X^2 Y+XY^2=0
XY(X Y +1+X+Y)=0
XY(X+1)(Y+1)=0