a)
7x(6x-5)² - (4x-3)(6x-5) - 2(6x-5)² =
= (6x - 5)[7x(6x-5) - (4x-3) - 2(6x-5)]
= (6x - 5)(42x² - 35x - 4x + 3 - 12x + 10)
= (6x - 5)(42x² - 51x + 13)
b)
5x(5x-2) - 2(5x-2) - 9 =
= (5x - 2)(5x - 2) - 9
= (5x - 2)² - 9
= (5x - 2 - 3)(5x - 2 + 3)
= (5x - 5)(5x + 1)
