Question 1099204
You want the other three roots of P?


If 2+4i is one root then 2-4i is also a root ....


The quadratic factor for these two roots is  {{{(x-2-4i)(x-2+4i)=((x-2)^2-i^2*16)}}}
{{{x^2-4x+4+16}}}
{{{x^2-4x+20}}}



Divide P(x) by  {{{x^2-4x+20}}} to find the other two roots.