iBooks Author Latex Question
iBooks Author only supports a subset of LaTeX, see iBooks Author: About LaTeX and MathML support for a full list of supported commands.

From looking at the samples in the support document, something like 

\begin{matrix}
1 &amp;  1 &amp;  1 \\
2 &amp; -1 &amp;  1 \\
1 &amp;  2 &amp; -1 \\
\end{matrix}


should work.