(−d−4cd−5c3)+(2c3+9d)

(-d - 4cd - 5c^3) + (2c^3 + 9d) = -d - 4cd - 5c^3 + 2c^3 + 9d = 9d - d - 4cd - 5c^3 + 2c^3 = (9d - d) - 4cd + (-5c^3 + 2c^3) = 8d - 4cd - 3c^3 = -3c^3 - 4cd + 8d

Ответ: -3c^3 - 4cd + 8d.