1) (x - 4)^2 - (x + 1)(x + 2)
(x + 5)^2- 5x(2 – x)
16y + 2(y – 4 )^2
2) 9y^2 – 25
4a - a^3
-5a^2- 10ab - 5b^2
3) (6x -x^2)^2 -x^2 (x – 3)(x + 3) + 6x(3 +2x^2)