Объяснение:

1) (8x - 5)(8x + 5) + 25 = 64x² - 25 + 25 = 64x²

2) (2b - 3)(2b + 3) - 4b² = 4b² - 9 - 4b² = -9

3) 9m² + (5 - 3m)(5 + 3m) = 9m² + 25 - 9m² = 25

4) (4a + 7)(7 - 4a) - 49 = -16a² + 49 - 49 = -16a²