1) (a + b)(c - d) = ac - ad + bc - bd;
2) (x - 6)(x - 4) = x² - 4x - 6x + 24 = x² - 10x + 24;
6) (3y - 5)(2y - 12) = 6y² - 36y - 10y + 60 = 6y² - 46y + 60;
7) (2x² - 3)(x² + 4) = 2x⁴ + 8x² - 3x² - 12 = 2x⁴ + 5x² - 12.