Answer
$-3i,-2,\frac{1}{3}$
Work Step by Step
Step 1. Given a zero $x=3i$, we know another zero is $x=-3i$, thus $(x+3i)(x-3i)=x^2+9$ is a factor.
Step 2. Perform a division as shown in the figure to get the quotient $3x^2+5x-2$ (one can also perform synthetic divisions to get the same result).
Step 3. Solve $3x^2+5x-2=0$ or $(3x-1)(x+2)=0$ to get $x=-2,\frac{1}{3}$
