Answer
$\{\pm\frac{\sqrt {15}}{3}, \pm i\sqrt 5\}$
Work Step by Step
Step 1. Let $u=x^2$, we have $3u^2+10u-25=0$
Step 2. Factor and solve: $(u+5)(3u-5)=0$ thus $u=-5, \frac{5}{3}$
Step 3. For $u=-5$, we have $x^2=-5$ and $x=\pm i\sqrt 5$
Step 4. For $u=\frac{5}{3}$, we have $x^2=\frac{5}{3}$ and $x=\pm\frac{\sqrt {15}}{3}$
Step 5. Thus we have the olution set $\{\pm\frac{\sqrt {15}}{3}, \pm i\sqrt 5\}$
