\leftroot - Used to fine-tune the placement of the index inside \sqrt or \root.
{ \leftroot }
\leftroot command is used to fine-tune the placement of the index inside \sqrt or \root.
\sqrt[3]{x}
\sqrt[3\leftroot1]{x}
\root 3\leftroot{-1} \of x
\root 3\leftroot{-1}\uproot2 \of x