Respuesta :

9x^4 - 6x^2 - 3x - 6

(9x^4-13x^3-x-7)+(7x^3-2x+1)  

Sort the terms by their powers, as x's with the same powers can be added together:

9x^4

-13x^3 + 7x^3 = -6x^3

-x - 2x = -3x

-7 +1  = -6

9x^4 - 6x^2 - 3x - 6