Add: (2x3−x2+4)+(x3+3x2−2x−1)(2x^3 - x^2 + 4) + (x^3 + 3x^2 - 2x - 1)(2x3−x2+4)+(x3+3x2−2x−1).
3x3+2x2−2x+33x^3 + 2x^2 - 2x + 33x3+2x2−2x+3
3x3−2x2+2x+33x^3 - 2x^2 + 2x + 33x3−2x2+2x+3
x3+4x2−2x+3x^3 + 4x^2 - 2x + 3x3+4x2−2x+3
3x3+2x2+2x+33x^3 + 2x^2 + 2x + 33x3+2x2+2x+3