Hey there!
To start, when you perform (f+g)(x), you are adding the functions together. This would mean, you would add 4x+9 to 4x^2. This should look like this:
(4x+9)+(4x^2)
Because there are no like terms, your final answer would be 4x+9+4x^2 or the last answer choice.
Hope this helps and have a marvelous day! :)
