Chapter 3, Polynomial and Rational Functions - Section 3.5 - Complex Zeros and the Fundamental Theorem of Algebra - 3.5 Exercises - Page 330: 39

$Q(x)=x^3-3x^2+4x-12$

The factor theorem says that if $f(c)=0$, then $(x-c)$ is a factor of $f(x)$ and if $(x-c)$ is a factor of $f(x)$, then $f(c)=0$. Using the known zeros, we construct the original function from the factors: $Q=(x-3)(x-2i)(x-(-2i))=x^3-3x^2+4x-12$