$$-6(4c-2)^2-4(4c-1) = -6(16c^2 - 16c + 4) - 16c + 4 = -96c^2 + 96c - 24 - 16c + 4 = -96c^2 + 80c - 20$$
Ответ: $$-96c^2 + 80c - 20$$