How do you write a polynomial function of least degree given the zeros -1, 2i?
Please see the explanation
The zero at -1 implies that (x + 1) is a factor:
The zero at 2i implies that (x - 2i) is a factor.
The zero at 2i implies that -2i is, also, a zero and, therefore, (x + 2i) is a factor.
We know that the product of complex conjugates
Use the F.O.I.L method to multiply:
Rearrange in descending power: