#### Answer

{$-8,27$}

#### Work Step by Step

Since, $u^2-u-6=0$
Factorize the expression as follows: $(u+2)(u-3)=0$
or, $u=${$-2,3$}
Replace $u$ with $x^{1/3}$, we have
$x^{1/3}=-2\implies x=-2^3$
$x=-8$
and $x^{1/3}=3\implies x=-3^3$
$x=27$
Hence, our solution set is $x=${$-8,27$}