Please help me with root problem.

[moronatmath]

Can someone please help me figure out how to do this problem? It is completely new to me. If I can work the problem out using a calculator that is preferred thank you!

The polynomial
f(x) = 9 x^3 - 2 x^2+ 81 x - 18
has 3 i as a root. Give all of the roots of f in a comma-separated list, including the given one.

Roots:

 

[Gene]

If 3i is a root, so is -3i.
That gives (x-3i)(x+3i) =(x²+9) as a factor. If you have a graphing calculator the x intercept of the original equation wouldbe the third root. Or you can practice your devision and find
(9x^3 - 2x^2+ 81x -18)/(x²+9)