Question 772260
The complex nonreal numbers come with their conjugates.

Form the factored form of the function:
{{{f(x)=(x-9)(x-(-i))(x-i)(x-(-6+i))(x-(-6-i))}}}
Fully multiply the expression...
...you may need some pre-simplifications first as well as later...
{{{f(x)=(x-9)(x+i)(x-i)(x+6-i)(x+6+i)}}}
{{{f(x)=(x-9)(x^2-i^2)((x+6)-i)((x+6)+i)}}}
{{{f(x)=(x-9)(x^2+1)((x+6)^2-i^2)}}}
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There is much more multiplying and simplifying to do, but at least I showed enough of the steps so you can see how to handle the complex roots and complex factors and begin their simplifications.  I post just that unfinished solution to the extent shown.