First, find the GCF
4 (x^2 + 9x + 18)
Then, find two numbers that multiply to 18 and add to 9. Your numbers should be 6 and 3. Separate and add x to each number to have a properly factored expression.
(x + 3)(x + 6)
Therefore, your answer should be x + 3 because that is one of your factors.
Hope this helps!
