Упростите выражение (9a-2) (9a+2) - 18a² 2) 25m² - (5m-7) (5m+7) 3) (b+7) (b-4) + (2b-6) (2b+6)

Упростим:

1) (9 * a - 2) * (9 * a + 2) - 18 * a² = (9 * a) ² - 2² - 18 * a² = 81 * a² - 18 * a² - 4 = a² * (81 - 18) - 4 = 63 * a² - 4;

2) 25 * m² - (5 * m - 7) * (5 * m + 7) = 25 * m² - (25 * m² - 49) = 25 * m² - 25 * m² + 49 = m² * (25 - 25) + 49 = 0 * m² + 49 = 49;

3) (b + 7) * (b - 4) + (2 * b - 6) * (2 * b + 6) = b² + 3 * b - 28 + 4 * b² - 36 = 5 * b² + 3 * b - 64.