Answer
$49w^8 -7r^2w^4 -30r^4$
Work Step by Step
We multiply each term of the first polynomial by each term of the second polynomial. Then we add the products, as follows
$$
(7w^4 - 6r^2)(7w^4 + 5r^2)=7w^4 (7w^4 + 5r^2)- 6r^2(7w^4 + 5r^2)\\
= 49w^8 +3 5w^4r^2-42r^2w^4 -30r^4\\
=49w^8 -7r^2w^4 -30r^4
.$$
