x²-x-y²-y= (x²-y²)-(x+y)= (x-y)(x+y)-(x+y)= (x+y)(x-y-1)
x² - x - y² - 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-y-1)
x² - x - y² - y = (x - y)(x + y) - (x + y) = (x + y)(x - y - 1)