Chapter 3 - Section 3.5 - Complex Zeros and the Fundamental Theorem of Algebra - 3.5 Exercises - Page 294: 59

$-3,\pm2i$

1. List possible rational zeros, 2. Use synthetic division, test these values from low to high, do not forget about multiplicity (m) of zeros. 3. It can be found that $x=3$ is a zero of $m=2$ as shown. 4 Reduce P to quadratic terms: $P=(x-3)^2(x^2+4)$ 5. Find all zeros: $-3,\pm2i$