We are given two binomials: x+4 , x^2-9.
x+4 can't be factored. Therefore, it is a prime.
Let us work on x^2-9.
9 could be written as 3^2.
Therefore, x^2-9 = x^2 - 3^2.
Now, we can apply difference of the squares formula to factor it.
We know a^2 -b^2 = (a-b) (a+b).
Therefore, x^2 - 3^2 can be factored as (x-3) (x+3).
So, x^2-9 is not a prime binomial because it can be factored as (x-3) (x+3).