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