$${{\mathtt{10}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{{\mathtt{x}}}^{{\mathtt{21}}} = {\mathtt{0}}$$
$${{\mathtt{x}}}^{{\mathtt{21}}} = -{\mathtt{100}}$$
x = $${\sqrt[{{\mathtt{{\mathtt{21}}}}}]{-{\mathtt{100}}}} = -{\mathtt{1.245\: \!197\: \!084\: \!735\: \!032\: \!8}}$$
$${{\mathtt{10}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{{\mathtt{x}}}^{{\mathtt{21}}} = {\mathtt{0}}$$
$${{\mathtt{x}}}^{{\mathtt{21}}} = -{\mathtt{100}}$$
x = $${\sqrt[{{\mathtt{{\mathtt{21}}}}}]{-{\mathtt{100}}}} = -{\mathtt{1.245\: \!197\: \!084\: \!735\: \!032\: \!8}}$$