(3 - 7n^4 + 6n^2) + (2n^2 + 8n^3 - 9) + (n^4 - 5n^3 - 4)

(3 - 7n^4 + 6n^2) + (2n^2 + 8n^3 - 9) + (n^4 - 5n^3 - 4)

3 - 7n^4 + 6n^2 + 2n^2 + 8n^3 - 9 + n^4 - 5n^3 - 4

3 - 9- 4 - 7n^4+ n^4 + 6n^2 + 2n^2 + 8n^3- 5n^3

-10 - 6n^4 + 8n^2 + 3n^3