(9n^2 - 6n^3 - 3n^4) - (7n^4 + 4) + (2n^3 + 8n^2)

(9n^2 - 6n^3 - 3n^4) - (7n^4 + 4) + (2n^3 + 8n^2)

9n^2 - 6n^3 - 3n^4 - 7n^4 - 4 + 2n^3 + 8n^2

9n^2+ 8n^2 - 6n^3+ 2n^3 - 3n^4 - 7n^4 - 4

17n^2 - 4n^3 - 10n^4 - 4