5. (10d² – 6d + 12) – (4d² + 3d – 5) + (d² – 2d)

5. $$(10d^2 - 6d + 12) - (4d^2 + 3d - 5) + (d^2 - 2d) = 10d^2 - 6d + 12 - 4d^2 - 3d + 5 + d^2 - 2d = 7d^2 - 11d + 17$$

Ответ: $$7d^2 - 11d + 17$$