1) (3a - 1)³ - 27a³ + 5 = 27a³ - 27a² + 9a - 1 - 27a³ + 5 = -27a² + 9a - 1
a = -1; => -27 - 9 - 1 = -37
a = 0; => 0 + 0 - 1 = -1
a = 1; => -27 + 9 - 1 = -19
2) (0.7b - 2)³ - (0.7b + 2)³ = (0.7b - 2 - 0.7b - 2)((0.7b - 2)² + (0.7b - 2)(0.7b + 2) + (0.7b + 2)²) = -4(0.49b² - 2.8b + 4 + 0.49b² - 4 + 0.49b² + 2.8b + 4) = -4(1.47b² + 4)
b = -2; => -39.52
b = -1; => -21.88
b = 1; => -21.88