Check if all roots of a polynomial have been found using Root?

[stevenrodriguez04 (Steven Rodriguez)]

Hi everyone, my name is Steven R. and this is my first time using Mathematica. I’m using it in school as of this semester. So I’m trying to see if what I got answers question B. I’m not sure how to tell if Mathematica recognizes these numbers as my roots of my polynomial function.

[danl (Daniel Lichtblau)]

It would be useful to post actual code rather than a screen shot.