Разложение на множители

a) $$25x^2 - y^2 = (5x)^2 - y^2 = (5x - y)(5x + y)$$

д) $$9m^2 - 16n^2 = (3m)^2 - (4n)^2 = (3m - 4n)(3m + 4n)$$

и) $$9 - b^2c^2 = 3^2 - (bc)^2 = (3 - bc)(3 + bc)$$