Question

find a polynomial f(x) of degree 3 with real coefficients and the following zeros -1,2i

Answer 1

anyone?

Answer 2

Use the Factor Theorem:

Factor Theorem, which states:
If f(a) = 0, then (x-a) is a factor of f(x).

So, if -1 is a zero, then (x - (-1)) = (x + 1) is a factor.

And, if 2i is a zero, then its conjugate, -2i, is a zero.
^^ Apply the Factor Theorem to them, also.l

Answer 3

the answer here isn't very clear

Answer 4

It is not an answer. It is a direction for your thinking.

In short, f(x) = (x + 1) * (x + 2i ) * (x - 2i ).