$\text{a) (x - 2)(x² - 2x + 4)(x + 2)(x² + 2x + 4) = 0}$

$\text{(x³ - 8)(x³ + 8) = 0}$

$\text{(x³)² - 8² = 0}$

$\text{x⁶ - 64 = 0}$

$\text{x⁶ = 64}$

$\text{x = ±2}$

$\text{b) (x + 4)(x² - 4x + 16) -x(x + 5)(x - 5) = 264}$

$\text{(x³ + 64) - x(x² - 25) = 264}$

$\text{(x³ + 64) - x³ + 25x = 264}$

$\text{x³ + 64 - x³ + 25x = 264}$

$\text{25x + 64 = 264}$

$\text{25x = 264 - 64}$

$\text{25x = 200}$

$\text{x = 8}$

$\text{c) (x - 2)³ - (x - 2)(x² + 2x + 4) = 6(x + 2)(2 - x)}$

$\text{(x - 2)³ - (x³ - 8) = -6(x + 2)(x - 2)}$

$\text{(x - 2)³ - (x³ - 8) = -6(x² - 4)}$

$\text{(x - 2)³ - (x³ - 8) = -6x² + 24}$

$\text{x³ - 6x² + 12x - 8 - x³ + 8 = -6x² + 24}$

$\text{x³ - 6x² + 12x - 8 - x³ + 8 + 6x² - 24 = 0}$

$\text{12x - 24 = 0}$

$\text{12x = 24}$

$\text{x = 2}$