\(={({x^{l - m}})^{({l^2} + lm + {m^2})}}{({x^{m - n}})^{{m^2} + nm + {n^2}}}\)\({({x^{n - l}})^{{n^2} + nl + {l^2}}}\)
\(={x^{{l^3} - {m^3}}}.{x^{{m^3} - {n^3}}}.{x^{{n^3} - {l^3}}}\)=\({x^{{l^3} - {m^3} + {m^3} - {n^3} + {n^3} - {l^3}}} = {x^0}=1\)