Answer
$36x^{7}-64x$
Work Step by Step
From Page 301, we know that the product of a sum and difference of two terms $x$ and $y$ is given by the following equation: $(x+y)(x-y)=x^{2}-y^{2}$.
Therefore, $4x(3x^{3}+4)(3x^{3}-4)=4x((3x^{3})^{2}-4^{2})=4x(3^{2}(x^{3})^{2}-16)=4x(9x^{6}-16)=36x^{7}-64x$.
