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