# Multline A group of equations

I have two equations. I use gather (or align) environment. one of the equations are too long and I want to multline them in that environment. How can I do it? and, How I can leftside these equations ?

\begin{gather}

8 \pi G a \bar{\alpha}+\acute{p} \partial \delta u  = - \dot{n} \partial E + a \partial\bar{A} \\
5000 \Pi K ( \delta\pi + 1.3 \delta p + \nabla \phi^S ) = -\frac{1000}{2.98 a^30} \nabla T - \frac{30 \dot{a}}{2 a} \dot{E} - \frac{\bar{t}}{a} \nabla \dot{F} - \frac{\dot{a}}{a^2} \nabla \bar{H} + \frac{3}{2} \ddot{C} + \frac{98.76 \dot{b}}{a} \dot{A} - \frac{J K \ddot{a}}{a} E + \frac{2}{9} \nabla \dot{B} + \frac{\dot{V}}{N} \nabla \dot{B}
\end{gather}


one possibilities is use multlined environment from package mathtools:

\documentclass[10pt]{amsart}
\usepackage{mathtools}

\begin{document}
\begin{gather}
8 \pi G a \bar{\rho}+\bar{p} \partial \delta u
= - \dot{a} \partial E + a \partial\dot{A}          \\
4 \pi K ( \delta\rho + 3 \delta p + \nabla \phi^S )
= \begin{multlined}[t][.5\textwidth]
-\frac{1}{2 a^2} \nabla T - \frac{3 \dot{a}}{2 a} \dot{E} - \frac{1}{a} \nabla \dot{F} - \frac{\dot{a}}{a^2} \nabla H \\
+ \frac{3}{2} \ddot{C} + \frac{3 \dot{b}}{a} \dot{A} - \frac{J K \ddot{a}}{a} E + \frac{2}{9} \nabla \dot{B} + \frac{\dot{a}}{a} \nabla \dot{B}
\end{multlined}
\end{gather}

\begin{align}
8 \pi G a \bar{\rho}+\bar{p} \partial \delta u
& = - \dot{a} \partial E + a \partial\dot{A}          \\
4 \pi K ( \delta\rho + 3 \delta p + \nabla \phi^S )
& = \begin{multlined}[t][.5\textwidth]
-\frac{1}{2 a^2} \nabla T - \frac{3 \dot{a}}{2 a} \dot{E} - \frac{1}{a} \nabla \dot{F} - \frac{\dot{a}}{a^2} \nabla H \\
+ \frac{3}{2} \ddot{C} + \frac{3 \dot{b}}{a} \dot{A} - \frac{J K \ddot{a}}{a} E + \frac{2}{9} \nabla \dot{B} + \frac{\dot{a}}{a} \nabla \dot{B}
\end{multlined}
\end{align}
\end{document}


here's one possibility:

\documentclass{article}
\usepackage{mathtools}
\begin{document}

\begin{gather}
8 \pi G a \bar{\rho}+\bar{p} \partial \delta u  = - \dot{a} \partial E + a \partial\dot{A} \\[\jot]
\begin{multlined}
4 \pi K ( \delta\rho + 3 \delta p + \nabla \phi^S )\\
= -\frac{1}{2 a^2} \nabla T - \frac{3 \dot{a}}{2 a} \dot{E} - \frac{1}{a} \nabla \dot{F} - \frac{\dot{a}}{a^2} \nabla H \\
\qquad {}+ \frac{3}{2} \ddot{C} + \frac{3 \dot{b}}{a} \dot{A} - \frac{J K \ddot{a}}{a} E + \frac{2}{9} \nabla \dot{B} + \frac{\dot{a}}{a} \nabla \dot{B}
\end{multlined}
\end{gather}

\end{document}


multlined is defined in mathtools; mathtools loads amsmath, so it's not necessary to mention that.

a small vertical space [1\jot] (defined by amsmath) is added after the first line to separate it a bit from the second equation.

and some space is added at the beginning of the last line so that the equals sign doesn't overlap. an empty group {} follows the space to ensure "binary" spacing of the plus at the beginning of the line.