Вариант 2. Задание 3. Разложите на множители: 1) (7m - n + 49m^2 - n^2); 2) (4x^2 - 4xy + y^2 - 16); 3) (xy^4 - 2y^4 - xy + 2y); 4) (9 - x^2 - 2xy - y^2).

**Решение:** 1) (7m - n + 49m^2 - n^2 = (7m - n) + (7m - n)(7m + n) = (7m - n)(1 + 7m + n)) 2) (4x^2 - 4xy + y^2 - 16 = (2x - y)^2 - 4^2 = (2x - y - 4)(2x - y + 4)) 3) (xy^4 - 2y^4 - xy + 2y = y^4(x - 2) - y(x - 2) = (x - 2)(y^4 - y) = y(x - 2)(y^3 - 1) = y(x - 2)(y - 1)(y^2 + y + 1)) 4) (9 - x^2 - 2xy - y^2 = 9 - (x^2 + 2xy + y^2) = 3^2 - (x + y)^2 = (3 - (x + y))(3 + (x + y)) = (3 - x - y)(3 + x + y))