Question

A polynomial with rational coefficients having roots 3, 3, and 3-i

Answer 1

Rational are Real

3-i must be accompanied by 3+i

Answer 2

suppose to write a function

Answer 3

Right. So do it.

Each root leads to a factor.

3 ==> (x-3)
3 ==> (x-3)
3+i ==> (x-(3+i))
3-i ==> (x-(3-i))

You have only some multiplication in your future.