i’ve tried to do it but i’m confused and need someone to show me.

From the given question,
[tex]x^4+9x^2[/tex]Now,
Put x=-3 into the given expression
[tex]x^4+9x^2=(-3)^4+9(-3)^2[/tex][tex]\begin{gathered} x^4+9x^2=(-3)^4+9(-3)^2 \\ =81+9(9) \\ =81+81 \\ =162 \end{gathered}[/tex]Hence, the option D is correct.