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