[tex]a^4+9a^2+81[/tex][tex]\begin{gathered} We\text{ can stil express the expressiona as} \\ a^4+(a^2\times3^2)+3^4 \\ \end{gathered}[/tex][tex]x^4+x^2y^2+y^4=\text{ }\frac{x^6-y^6}{x^2-y^2}[/tex][tex]\begin{gathered} =\frac{(x^2)^3-(y^2)^3}{x^2-y^2} \\ =\frac{(a^2)^3-(3^2)^3}{a^2-3^2} \end{gathered}[/tex][tex]\begin{gathered} \\ =\frac{a^6-3^6^{}}{a^2-3^2} \\ =\frac{(a^3-3^3)(a^3+3^3)}{(a-3)(a+3)} \end{gathered}[/tex][tex](a^2+3a+9)(a^2-3a+9)[/tex]
