The problem asks to simplify the expression $(x^2+9y^2)(x+3y)(x-3y)$.

1. Problem Description

The problem asks to simplify the expression $(x^2+9y^2)(x+3y)(x-3y)$.

2. Solution Steps

First, we multiply the factors $(x+3y)$ and $(x-3y)$. This is a difference of squares.

$(x+3y)(x-3y) = x^2 - (3y)^2 = x^2 - 9y^2$

Now we multiply this result by the remaining factor $(x^2+9y^2)$.

$(x^2+9y^2)(x^2-9y^2) = (x^2)^2 - (9y^2)^2$

This is again a difference of squares.

$= x^4 - 81y^4$

3. Final Answer

$x^4 - 81y^4$