Раскрой скобки а) (x-5)*(x+5) б) (7c+3)*(7c-3) в) (4x-9y)*(4x+9y)

a) (x-5) * (x+5) = x^2 - 5x + 5x - 25 = x^2 - 25

б) (7c + 3) * (7c - 3) = 49c^2 - 3^2 = 49c^2 - 9

в) (4x - 9y) * (4x + 9y) = 16x^2 - 9y^2