Respuesta :
first remove the 2 sets of parentheses. The signs of the terms in the second parentheses will stay the same because the sign in front is positive. So we have:-
9x^3 - 4x^2 + 2x + 3 - 5x^3 + 7x^2 - 6x + 5
= 4x^3 + 3x^2 - 4x + 8
9x^3 - 4x^2 + 2x + 3 - 5x^3 + 7x^2 - 6x + 5
= 4x^3 + 3x^2 - 4x + 8
