Answer:
81y^4 - 16x^2, difference of squares.
Step-by-step explanation:
So we need to expand the following product:
(9y2-4x)(9y2+4x) = 9y2*9y2 + 4x*9y2 - 4x*9y2 -4x*4x = 81y^4 - 16x^2
And this type of product is the difference of squares.
First you do x multiply 2x to get 2x^2
then you do x multiply-3 to get -3x
then 5 multiply 2x so you get 10x
then you do 5 multiply-3 to get -15
then you join it together to get
2x^2+10x-3x-15
then simply to get 2x^2+7x-15
and that should be your answer