Find the product −

To find the product, we will use distributive law as follows:​

$-3 y\left(x y+y^{2}\right)$

$=-3 y \times x y+(-3 y) \times y^{2}$

$=-3 x y^{1+1}-3 y^{1+2}$

$=-3 x y^{2}-3 y^{3}$

Substituting x = 4 and y = 5 in the result, we get:

$-3 x y^{2}-3 y^{3}$

$=-3(4)(5)^{2}-3(5)^{3}$

$=-3(4)(25)-3(125)$

$=-300-375$

$=-675$

Thus, the product is $\left(-3 x y^{2}-3 y^{3}\right)$, and its value for $x=4$ and $y=5$ is $(-675)$.