If one zero is A+Bi, then A-Bi is also a zero.

So since one zero is -i, then +i is also a zero.

And since one zero is 3+i, then 3-i is also a zero.

So these are the 5 zeros:

   x=-2,  x=-i;   x=+i;   x=3+i;   x=3-i

Get 0 on the right of all 5 equations:

 x+2=0;  x+i=0;  x-i=0; x-3-i=0; x-3+i=0

Multiply both sides of all those 5 equations together:

 (x+2)(x+i)(x-i)(x-3-i)(x-3+i) = 0

Multiply all those together (it's a lot of work) and set f(x)
equal to what you get.  If you have trouble, tell me in the 
thank you note
form below and I'll get back to you by email.  No charge ever.
I do this as a hobby.

Edwin