(3x^3-4x^2-5x+3)+(-4 - 6x^3+x^2 - 5x+5)
(3x^3-4x^2-5x+3)+(-4 - 6x^3+x^2 - 5x+5)= 3x^3 - 4x^2 - 5x + 3 - 4 - 6x^3 + x^2 - 5x + 5= -3x^3 - 3x^2 - 10x + 4
= -3x^3 - 3x^2 - 10x + 4 is the correct answer
