我如何对齐分解的方程式？

Question

如何将子方程与其间的文本对齐？

\documentclass{article}
\usepackage{amsmath}

\begin{document}

Foo.

\begin{subequations}
\begin{equation} \label{eq:f}
    \begin{aligned}
        A &=10000000000000000 + -1 + -10000000000000000000000 \\
        &= 10000000000000000000000  + 10000000000000000000000 + -1
    \end{aligned}
\end{equation}

\begin{equation} \label{eq:oo}
    \begin{aligned}
        A &=10000000000000000 + -1 + -100000000000 \\
        &= 1 + 10000000000000000000000 + -1
    \end{aligned}
\end{equation}

Bar.

\begin{equation} \label{eq:ar}
    \begin{aligned}
        A &=1 + -1 + -1 \\
        &= 1 + 1 + -1
    \end{aligned}
\end{equation}
\end{subequations}

Foobar.

\end{document}

Answer 1

这是一种可能性，具有单一align环境和\intertext：

\documentclass{article}
\usepackage{mathtools}

\begin{document}

\noindent Foo.
\begin{subequations}
\begin{align}
        A &=10000000000000000 + -1 + -10000000000000000000000 \notag\\
        &= 10000000000000000000000 + 10000000000000000000000 + -1 \label{eq:f} \\[1ex]
        A &=10000000000000000 + -1 + -100000000000 \notag\\
        &= 1 + 10000000000000000000000 + -1 \label{eq:oo} \\[1ex]
\shortintertext{Bar. \vskip 1ex}
        A &=1 + -1 + -1 \notag \\
        &= 1 + 1 + -1 \label{eq:ar}
\end{align}
Foobar.
\end{subequations}

\end{document}