Find the sum and express it in the simplest form. (2y^2+9y+4) + (-3y^2-3y-9)

Since the operation between the two sets of parentheses is addition, we don't have to do anything with it, and can remove the parentheses.

Our new expression is: 2y^2+9y+4-3y^2-3y-9

Now, we just add like terms together to solve for the simplest form of the expression.

2y^2+9y+4-3y^2-3y-9

(2-3) y^2 + (9-3) y + (4-9)

-y^2+6y-5

Our final answer is - y^2+6y-5.