Answer
$\{-\frac{1}{27}, \frac{1}{8}\}$
Work Step by Step
Step 1. Let $u=(x)^{-1/3}$, we have $u^2+u-6=0$
Step 2. Factor and solve: $(u-2)(u+3)=0$ thus $u=-3, 2$
Step 3. For $u=-3$, we have $(x)^{-1/3}=-3$ thus $x=-\frac{1}{27}$
Step 4. For $u=2$, we have $(x)^{-1/3}=2$ thus $x=\frac{1}{8}$
Step 5. Solution set $\{-\frac{1}{27}, \frac{1}{8}\}$