a)
(x -2)(x + 2) - (x + 4)^2 + (2x - 4)^2 = x^2 + 2x - 2x - 0 - (x^2 + 16) + (2x^2 - 16) = x^2 + 2x - 2x - x^2 - 16 + 2x^2 - 16 = 2x^2 + 0 - 32 = 2x^2 - 32
b)
- (-2x - 6)^2 - (-3x - 4)^2 = (-2x + 6)^2 - (3x + 4)^2 = -2x^2 + 36 - 3x^2 + 16 = -5x^2 + 52
