Answer:
To find the sum of the two expressions, we can combine like terms. In this case, we have two terms with a coefficient of -3y² and two terms with a coefficient of -3y, so we can combine them to get:
(-3y² + -3y²) + (-3y + -3y) + (2y² + 9y + 4)
Simplifying the expression gives us:
-6y² - 6y + 2y² + 9y + 4
Combining the like terms again gives us:
-4y² + 15y + 4
Therefore, the sum of the two expressions is -4y² + 15y + 4. This is already in simplest form.