(7x^3+ 6x^2 + x -1) + (9x^3 +4x^2 -x+10)

(7x^3+ 6x^2+ x -1) + (9x^3 +4x^2 -x+10)

7x^3+ 6x^2+ x -1 + 9x^3 +4x^2 -x+10

7x^3+9x^3 +6x^2+4x^2 +x-x -1+10

16x^3 +10x^2 +9