1) (a + 3)(a - 2) + (a - 3)(a + 6) = a² - 2a + 3a - 6 + a² + 6a - 3a - 18 = 2a² + 4a - 24 = 2(a² + 2a - 12)
2) (x - 2)² + (x - 1)(x + 1) = x² - 4x + 4 + x² - 1 = 2x² - 4x + 3
3) (3a - 2b)(3a + 2b) - (a + 3b) = 9a² - 4b² - a - 3b
