Question 977234
Try synthetic division to test for the  possible roots, plus or minus 1,3,9.  The quadratic result of the first found root can then be finished using general solution for a quadratic equation.


Testing  -3,
Find quotient, {{{x^2-9}}}.


That tells you because of further obvious factorability of the resulting quotient,
{{{(x+3)(x+3)(x-3)=P(x)}}}
Roots are -3 and +3.  The  -3 root is of multiplicity two.