Hey there!
Your answer would be (n+3)(n+3) because you're trying to factor the polynomial as simply as possible so you first factor the first and last terms which are 1 and 9 and then find the numbers from 9 that add up to 6 which would be 3+3 and then you can factor by using the Square of a Sum equation which is a^2+ 2ab+ b^2= (a+b)^2 and you will end up getting (n+3)(n+3) or (n+3)^2.
Hope this helps you out!