Verified answer

(a - 4)(a + 4) = a² - 4² = a² - 16

(5x + y)(y - 5x) = y² - (5x)² = y² - 25x²

(1 - x³)(1 + x³) = 1² - (x³)² = 1 - x⁶

(14 + x)(x - 14) = x² - 14² = x² - 196

(5a + 3b)(3b - 5a) = (3b)² - (5a)² = 9b² - 25a²

(10x + 0,3)(0,3 - 10x) = 0,3² - (10x)² = 0,09 - 100x²

(x + 3)(x - 3)(x² + 9) = (x² - 9)(x² + 9) = (x²)² - 9² = x⁴ - 81