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

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

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

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

15r^2 - 9r^4 - 2r^3 +9r