Math & Science ⇒ Multi-line Part of Numbered Equation

[StarKid]

I need to reproduce the numbered equation in the attachment. The problem is the multi-line part inside the curly braces. If I use the align environment, both lines get numbered. If I use {equation}, the \\ used to split the lines isn't recognized. If I use {displaymath}, the entire equation will not be numbered at all. I tried multline, and I received an error for the curly braces around the multi-line part (tried {} as well as \left\lbrace and \right\rbrace. What can I use?

[kaiserkarl13]

This will work:

Code: Select all

\documentclass[leqno]{article}
\begin{document}
  \begin{equation}
    \theta P_t + \sum_{j=1}^{\infty}
        \left(\frac{1-\delta}{1+\rho_t^{t+j}}\right)^j
        \frac{1}{1-\delta}
        \left\{
            \begin{array}{c}
                r_{t+j} (1-\phi)(1-\theta)P_t + \tau (1+g)^{j-1} P_t \\
                -\delta\left[P_{t+j} - (1-\theta) P_t\right]
            \end{array}
        \right\}
  \end{equation}
\end{document}

If you don't like the spacing that the array environment uses, try using one of AMSLaTeX's environments, gathered, aligned, and alignedat. For example,

Code: Select all

\documentclass[leqno]{article}
\usepackage{amsmath}
\begin{document}
  \begin{equation}
    \theta P_t + \sum_{j=1}^{\infty}
        \left(\frac{1-\delta}{1+\rho_t^{t+j}}\right)^j
        \frac{1}{1-\delta}
        \left\{
            \begin{gathered}
                r_{t+j} (1-\phi)(1-\theta)P_t + \tau (1+g)^{j-1} P_t \\
                -\delta\left[P_{t+j} - (1-\theta) P_t\right]
            \end{gathered}
        \right\}
  \end{equation}
\end{document}