Expand and simplify the following: (9y-9)(6y+4)

To expand and simplify the expression (9y-9)(6y+4), we use the distributive property:

(9y-9)(6y+4)
= 9y(6y) + 9y(4) - 9(6y) - 9(4)
= 54y^2 + 36y - 54y - 36
= 54y^2 - 18y - 36

So, the simplified expression is 54y^2 - 18y - 36.