Okay, here we have this:
We need to solve ans simplify: (3b+6)(3b-6)(9b^2-36) , let's do it:
[tex]\begin{gathered} \mleft(3b+6\mright)\mleft(3b-6\mright)\mleft(9b^2-36\mright) \\ =((3b^{})^5-6^2)(9b^2-36) \\ =(9b^2-36)(9b^2-36) \\ =(9b^2-36)^2 \\ =(9b^2)^2-2\cdot36\cdot9b^2+36^2 \\ =81b^4-648b^2+1296 \end{gathered}[/tex]