Question: I have two equations in the `\gathered` environment.

```
\documentclass{book} 
  \usepackage{amsmath}

 \begin{document}  

\begin{equation} 
 \begin{gathered}
     \Delta U_{ab}+\Delta U_{ba}=0\\
    \int_{\vec r_a}^{\vec r_b}\vec F\cdot d\vec r +\int_{\vec r_b}^{\vec r_a}\vec F\cdot d\vec r=0
     \label{ce23}  

  \end{gathered} 
 \end{equation}

 \end{document}

```

Producing the output:

[![enter image description here](https://i.stack.imgur.com/ugGiW.png)](https://i.stack.imgur.com/ugGiW.png)

But instead, I want the following output using `\gathered` itself, instead of `\align` which I used for this MWE

[![enter image description here](https://i.stack.imgur.com/NwSDR.png)](https://i.stack.imgur.com/NwSDR.png)

Code for which is

```
   \documentclass{book} 
      \usepackage{amsmath}

     \begin{document}  

     \begin{align}
         \Delta U_{ab}&+\Delta U_{ba}=0 \nonumber\\
        \int_{\vec r_a}^{\vec r_b}\vec F\cdot d\vec r &+\int_{\vec r_b}^{\vec r_a}\vec F\cdot d\vec r=0
         \label{ce23}  
      \end{align} 

     \end{document}

```

Answer: 
Just use `gather` instead of `gathered`.

[![](https://i.stack.imgur.com/qYQO0.png)](https://i.stack.imgur.com/qYQO0.png)

```
\documentclass{book} 
\usepackage{amsmath}

\begin{document}  

\begin{gather}
    \Delta U_{ab}+\Delta U_{ba}=0 \nonumber\\
    \int_{\vec r_a}^{\vec r_b}\vec F\cdot d\vec r +\int_{\vec r_b}^{\vec r_a}\vec F\cdot d\vec r=0
    \label{ce23}
\end{gather}

\end{document}

```
It's better to use `gathered`, if possible, so TeX is able to use short vertical skips in case the line preceding the display is short. Compare the two otherwise identical displays: the space surrounding the second one is too wide.

The key is `\begin{gathered}[b]`.

```
\documentclass{book}
\usepackage{amsmath}

\usepackage{lipsum}

\begin{document}

\lipsum[1][1-3]
\begin{equation}\label{ce23}
\begin{gathered}[b]
  \Delta U_{ab}+\Delta U_{ba}=0 \\
  \int_{\vec{r}_a}^{\vec{r}_b}\vec{F}\cdot d\vec{r}
  +\int_{\vec{r}_b}^{\vec{r}_a}\vec{F}\cdot d\vec{r}=0
\end{gathered}
\end{equation}
\lipsum[2][1-3]

\lipsum[1][1-3]
\begin{gather}
  \Delta U_{ab}+\Delta U_{ba}=0 \notag \\
  \int_{\vec{r}_a}^{\vec{r}_b}\vec{F}\cdot d\vec{r} 
  +\int_{\vec{r}_b}^{\vec{r}_a}\vec{F}\cdot d\vec{r}=0
  \label{ce23bad}
\end{gather}
\lipsum[2][1-3]

\end{document}

```

[![enter image description here](https://i.stack.imgur.com/Zs5Y2.png)](https://i.stack.imgur.com/Zs5Y2.png)

I changed all `\vec r` and similar into the better `\vec{r}`, not more difficult to type and definitely clearer.