Вправи: 725

725. Виконайте множення:

1) (c + 7)(7 – c) = (7 + c)(7 – c) = 49 – c²;

2) (0,5m – 3)(0,5m + 3) = 0,25m² – 9;

3) (3k + 7)(3k – 7) = 9k² – 49;

4) (2р – 9q)(9q + 2p) = (2p – 9q)(2p + 9q) = 4p² – 81q²;

5) (10m + 9n)(9n – 10m) = (9n + 10m)(9n – 10m) = 81n² – 100m²;

6) (23c – 45d)(23c + 45d) = (23c)² – (45d)² = 49c² – 1625d².