lets start over with this problem:
n^2 - 9n + 9
how do you determine if this is a perfect square, and can you factor it?
I posted two answers below the two you got.
n^2 - 9 n + 81/4 = (n-9/2)^2
would be a perfect square
n^2 - 6 n + 9 = (n-3)^2
would be a perfect square
You can not factor n^2 - 9 n + 9