Answer:
Step-by-step explanation:
Since the leading coefficient is 1, we list the factors of the last term (-27) as the list of possible rational roots. Write the plus minus version of each.
If you don't want to use the plus minus symbol, then the list could look like this:
-1, 1, -3, 3, -9, 9, -27, 27
Optionally you could sort from smallest to largest, but I think it's handy to keep the corresponding pairs together.