(b + 6)(b - 6) - 3(b + 2) = b² - 36 - 3b - 6 = b² - 3b - 42
(3a - 2)(3a + 2) + (a - 8)(a + 8) = 9a² - 4 + a² - 64 = 10a² - 68
(5x - 3y)(5x + 3y) + (3x - 5y)(3x + 5y) = 25x² - 9y² + 9x² - 25y² = 34x² - 34y²
(c - 2)(3 - c) - (5 - c)(5 + c) = 3c - 6 - c² + 2c - 25 + c² = 5c - 31