Write a polynomial equation in standard form with the given zeros -5, 2i

Answer 1

Implied is that the coefficients are real. This means that, if 2i is a root, so is -2i (the complex conjugate)

(x + 5) (x - 2i) (x + 2i) = (x + 5) (x² + 4) = x³ + 5x² + 4x + 20