The roots are
[tex]\begin{gathered} x=3 \\ x=4i \\ x=-4i \end{gathered}[/tex]The polynomial can be modellled as ;
[tex]f(x)=a(x-3)(x-4i)(x+4i)[/tex][tex]f(x)=a(x-3)(x^2+16)[/tex]
Let us use f(2) to obtain a value for a
[tex]\begin{gathered} f(2)=a(2-3)(2^2+16) \\ 40=-20a \\ a=-2 \end{gathered}[/tex]The polynomal f(x) is given as
[tex]\begin{gathered} f(x)=-2(x-3)(x^2+16) \\ f(x)=-2x^3+6x^2-32x+96 \end{gathered}[/tex]