(x + 8y)² - (8x + y)² = (x + 8y - 8x - y)(x + 8y + 8x + y) = (- 7x + 7y)(9x + 9y) =
= 7 * 9 * ( - x + y)(x + y) = 63(- x + y)*(x + y)
(x + 8y)² - (8x + y)² = (x + 8y - 8x - y)(x + 8y + 8x + y) = (- 7x + 7y)(9x + 9y) =
= 7 * 9 * ( - x + y)(x + y) = 63(- x + y)*(x + y)