Verified answer

8x - 8y - ax + ay = 8(x - y) - a(x - y) = (8 - a)(x - y) = (x - y)(8 - a)

a(b - c) - (c - b) = a(b - c) + (b - c) = (a + 1)(b - c)

(x - y)² - a(y - x) = (x - y)² + a(x - y) = (x - y)(x - y + a)

(x - y)² - a(y - x) = (y - x)² - a(y - x) = (y - x)(y - x - a)