Roots

The \sqrt command accepts two arguments. The first, and optional, argument specifies what order of root you desire if it is anything other than the square root. The second, and mandatory, argument specifies the expression that the root sign should enclose:

\begin{mathegs}
\verb@$\sqrt{a+b}$@ & $\displaystyle\sqrt{a+b}$\\
\verb@$\sqrt[...
...[3]{x^3+1}}$@ & $\displaystyle\frac{\sqrt{x+1}} {\sqrt[3]{x^3+1}}$
\end{mathegs}