First observe that a cubic has at least one real root. So if all the rootsOriginally Posted byunicorn

lie on then should be a real root.

This checks out, so we know that is a factor of the cubic,

and so we use long division to find the remaining quadratic factor:

Now we can use that quadratic formula to verify that the two remaining

roots (which are the roots of ) have real parts

(which they do).

RonL