Replace x3 by t.
Therefore,
\left|t-1 \right|+\left|2-t \right|=1
For t\leq1 ,
t=1
For 1<t<2 , the equation is satisfied \forall \: t \in \left(1,2 \right).
For t\geq2 ,
t=2
Then, solution set is given by \left\{f(x):f(x)=x^{\frac{1}{3}}, f:\left[1,2 \right]\rightarrow \mathbb{R} \right\}