4x²-4xy+y²-16 = (2x)² - 2·2x·y + y² - 16 = (2x - y)² - 16 = (2x - y - 4)(2x - y + 4)
x - 2 - xy + 2y = x(1 - y) - 2(1 - y) = (1 - y)(x - 2)
4x²-4xy+y²-16 = (2x)² - 2·2x·y + y² - 16 = (2x - y)² - 16 = (2x - y - 4)(2x - y + 4)
x - 2 - xy + 2y = x(1 - y) - 2(1 - y) = (1 - y)(x - 2)