Answer :
[tex]2x^3+x^2-18x-9=x^2(2x+1)-9(2x+1)\\\\=(2x+1)(x^2-9)=(2x+1)(x^2-3^2)\\\\=(2x+1)(x-3)(x+3)[/tex]
[tex]2x^3 + x^2 - 18x - 9=x^2(2x+1)-9(2x+1)=\\ \\=(2x+1)(x^2-9)=(2x+1)(x-3)(x+3)[/tex]