The other two options are (x -5) or (x + 1).
The best way to go about finding this is by dividing. You can do this through synthetic division or by long division.
After dividing by x + 3, you'll be left with x^2 - 4x - 5, which can be factored. To factor, always check factors of the last number that add to the middle number. The factors of -5 are either 1 and -5 or 5 and -1. Since the first pair add to the middle coefficient, use those in the parenthesis.