19. 7,29x⁶ - 7,84y⁶ = (√7,29x³)² - (√7,84y³)² = (2,7x³)² - (2,8y³)² = (2,7x³ - 2,8y³)(2,7x³ + 2,8y³)
Ответ: (2,7x³ - 2,8y³)(2,7x³ + 2,8y³)