+33663 If this is 5√(-13.7) then the only real number answer is
$${\mathtt{\,-\,}}\left({{\mathtt{13.7}}}^{\left({\frac{{\mathtt{1}}}{{\mathtt{5}}}}\right)}\right) = -{\mathtt{1.687\: \!889\: \!896\: \!014\: \!528\: \!1}}$$
Check
$${\left(-{\mathtt{1.687\: \!889\: \!896\: \!014\: \!528\: \!1}}\right)}^{{\mathtt{5}}} = {\mathtt{\,-\,}}{\frac{{\mathtt{137}}}{{\mathtt{10}}}} = -{\mathtt{13.700\: \!000\: \!000\: \!000\: \!000\: \!5}}$$
Ok (apart from small numerical rounding error in the decimal representation)
+33663 If this is 5√(-13.7) then the only real number answer is
$${\mathtt{\,-\,}}\left({{\mathtt{13.7}}}^{\left({\frac{{\mathtt{1}}}{{\mathtt{5}}}}\right)}\right) = -{\mathtt{1.687\: \!889\: \!896\: \!014\: \!528\: \!1}}$$
Check
$${\left(-{\mathtt{1.687\: \!889\: \!896\: \!014\: \!528\: \!1}}\right)}^{{\mathtt{5}}} = {\mathtt{\,-\,}}{\frac{{\mathtt{137}}}{{\mathtt{10}}}} = -{\mathtt{13.700\: \!000\: \!000\: \!000\: \!000\: \!5}}$$
Ok (apart from small numerical rounding error in the decimal representation)
