Answer
$7w^4y-28w^2y^3+42w^4y^4.$
Work Step by Step
By multiplying each term of the polynomial by the factor $7w^2y$, and then adding the products, we have
$$
7w^2y(w^2 - 4y^2 + 6w^2y^3)=7w^2y(w^2 )+7w^2y(- 4y^2) +7w^2y( 6w^2y^3)\\
=7w^4y-28w^2y^3+42w^4y^4.
$$
