1) (a + 7)² = a² + 2*a*7 + 7² = a² + 14a + 49
2) (3x - 4y)² = (3x)² - 2*3x*4y + (4y)² = 9x² - 24xy + 16y²
3) (m - 6)(m + 6) = m² - 6² = m² - 36
4) (5a + 8b)(8b - 5a) = (8b + 5a)(8b - 5a) = (8b)² - (5a)² = 64b² - 25a²