Answer
$4k^{4}-36h^{2}$
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, $(2k^{2}+6h)(2k^{2}-6h)=(2k^{2})^{2}-(6h)^{2}=2^{2}(k^{2})^{2}-6^{2}h^{2}=4k^{4}-36h^{2}$.
