\(=\left(x-x\right)^2+\left(y-y\right)^2=0^2+0^2=1+1=2\)
\(x^2-x-y^2-y\)
\(=\left(x^2-y^2\right)-\left(x+y\right)\)
\(=\left(x-y\right)\left(x+y\right)-\left(x+y\right)\)
\(=\left(x+y\right)\left(x-y-1\right)\)
x2 - x + y2 - y = x . x - x + y . y - y
= 2x + 2y
= 2(x + y)