3. Разложите на множители: 1) a²-36b² + a - 6b; 2) 25x²- 10xy + y² - 9; 3) ay + y² - ay³ - y³; 4) 4-m² + 14mn - 49n².

1) $$a^2 - 36b^2 + a - 6b = (a - 6b)(a + 6b) + (a - 6b) = (a - 6b)(a + 6b + 1)$$

2) $$25x^2 - 10xy + y^2 - 9 = (5x - y)^2 - 3^2 = (5x - y - 3)(5x - y + 3)$$

3) $$ay^7 + y^7 - ay^3 - y^3 = y^7(a + 1) - y^3(a + 1) = (a + 1)(y^7 - y^3) = (a + 1)y^3(y^4 - 1) = (a + 1)y^3(y^2 - 1)(y^2 + 1) = (a + 1)y^3(y - 1)(y + 1)(y^2 + 1)$$

4) $$4 - m^2 + 14mn - 49n^2 = 4 - (m^2 - 14mn + 49n^2) = 4 - (m - 7n)^2 = 2^2 - (m - 7n)^2 = (2 - (m - 7n))(2 + (m - 7n)) = (2 - m + 7n)(2 + m - 7n)$$