equation

Synopsis:

\begin{equation}
  mathematical text
\end{equation}

The same as a displaymath environment (see displaymath) except that LaTeX puts an equation number flush to the right margin. The equation number is generated using the equation counter.

You should have no blank lines between \begin{equation} and \begin{equation}, or LaTeX will tell you that there is a missing dollar sign.

The package amsmath package has extensive displayed equation facilities. New documents should include this package.