Answer
$24x^2-54y^2$
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
$$
(4x - 6y)(6x + 9y)=4x (6x + 9y)- 6y(6x + 9y)\\
=24x^2+36xy-36xy-54y^2=24x^2-54y^2
.$$
