fully expand and simplify

(-9y + 3) (5y + 5)

First, let's expand the given expression:

(-9y + 3) (5y + 5)
= -9y(5y) - 9y(5) + 3(5y) + 3(5)
= -45y^2 - 45y + 15y + 15
= -45y^2 - 30y + 15

Next, we can simplify this expression by combining like terms:

-45y^2 - 30y + 15

Therefore, the fully expanded and simplified form of the expression (-9y + 3) (5y + 5) is -45y^2 - 30y + 15.