[tex](2x^2- x+3)(2x^2-x-1) = \Big[(2x^2- x)+3\Big]\Big[(2x^2-x)-1\Big]= \\ =\Big[(2x^2-x)(2x^2-x) -(2x^2-x)+3(2x^2-x) - 3\Big] = \\ =(2x^2-x)^2-2x^2+x+6x^2-3x-3 = \\ =4x^4-4x^3+x^2-2x^2+6x^2-2x-3 = 4x^4-4x^3+5x^2-2x-3 \\ \\ \center sau[/tex]
[tex](2x^2- x+3)(2x^2-x-1) = \\ =4x^4-2x^3-2x^2-2x^3+x^2+x+6x^2-3x-3= \\ =4x^4-4x^3+5x^2-2x-3[/tex]
