Math & Science ⇒ Simple math problem

[exactos]

I don't know what's the problem with the following code. Help!!

Code: Select all

\begin{displaymath}

\textit{Price_{ij}-P^{t}= \mathop
\mathrm{\mu}+e_{i}+\beta{}_{1}PCM_{i}+ \beta{}_{2}Power_{i}
+\beta{}_{3}PCM_{i}}\times{}\textit{Power_{i} + \beta{}_{4}First_{i}
+ \beta{}_{5}Second_{i}
+\beta{}_{6}PCM_{i}}\times{}\textit{First_{i}+
\beta{}_{7}PCM_{i}}\times{}\textit{Second_{i} +
\beta{}_{8}Power_{i}}\times{}\textit{First_{i}+
\beta{}_{9}Power_{i}}\times{}\textit{Second_{i} +
\beta{}_{10}PCM_{i}}\times{}\textit{Power_{i}}\times{}\textit{First_{i}+
\beta{}_{11}PCM_{i}}\times{}\textit{Power_{i}}\times{}\textit{Second_{i}
+\epsilon{}_{ij};}

\end{displaymath}

[CrazyHorse]

I don't know what's the problem with the following code.

Code: Select all

\documentclass{article}
\usepackage{amsmath}
\pagestyle{empty}


\begin{document}

\begin{flalign*}
\textit{Price}_{ij}-P^t = \mu+e_{i} &+ \beta_1 \textit{PCM}_{i}+ \beta_2 \textit{Power}_{i}
+\beta_3\textit{PCM}_i\times\textit{Power}_i + \beta_4\textit{First}_i
+\beta_5\textit{Second}_i \\
  & 
  +\beta_6 PCM_i\times\textit{First}_i+
   \beta_7PCM_i\times\textit{Second}_i +
   \beta_8Power_i\times\textit{First}_i\\
  & 
  +\beta_9Power_i\times\textit{Second}_i +
   \beta_{10}PCM_i\times\textit{Power}_i\times\textit{First}_i\\
  & 
  +\beta_{11}\textit{PCM}_i\times\textit{Power}_i\times\textit{Second}_i
  +\epsilon_{ij};
\end{flalign*}

\end{document}

Herbert