1) 4a² - 4ab - 4a² +ab - 4ab + b² = b² - 7ab
2) 5c² + 10c - 3c - 6 + 2c - 5c² - 8 + 20c = 29c - 14
3) (x² - x + 1)(x² + x - 1) = x⁴ + x³ - x² - x³ - x² + x + x² + x - 1 = x⁴ - x² + 2x - 1
4) (c-1)(c⁴ - c³ + c² - c + 1) = c⁵ - c⁴ + c³ - c² + c - c⁴ + c³ - c² + c - 1 = c⁵ - 2c⁴ + 2c³ - 2c² + 2c - 1