(3x^3+3x+1)(3^3-3x+1)-(3x^3+1)^2
=3x^3(3^3-3x+1)+3x(3^3-3x+1)+1(3^3-3x+1)-(3x^3)^2+2.3x^3.1+1^2
=3^4x^3-3^2x^4+3x^3+3^4x-3^2x^2+3x+3^3-3x+1-3^2x^6+6x^3+1
=(3^4x^3+3x^3)-(3^2x^4-3^2x^6-3^2x^2)+(3^4+3^3+1+1+1-3^2)+(3x-3x-3x)
=x^3(3^4+3)-3^2(x^4-x^6-x^2)+102-3x
=84x^3-9.(x^4-x^6-x^2)+102-3x