[Tex/LaTex] Equation number format in Appendix

Question

\documentclass[preprint,12pt,sort&compress]{elsarticle}

\begin{document}

\section{Introduction}
bla bla bla...

\section{Formulation}

\appendix
\section{}
The advection eq is... 
\begin{equation}
u_t+au_x&=&0,
\end{equation}

\end{document}

In Section formulation, Equation number is 1, and in Appendix Equation number is A.1.
I want to continue the equation number in Appendix i.e numbers must be 2.
I also tried

\begin{appendices}
...
\end{appendices}

then equation numbering is okay (i.e 2) but the main heading is Appendices instead of Appendix.
I want main section as a title 'Appendix' and equation number must be continue from previous section.

your cooperation will be appreciated.

Thank you in advance.

Bibigul

Answer 1

With the appendices environment:

\documentclass[preprint,12pt,sort&compress]{elsarticle}
\usepackage[page]{appendix}
\renewcommand{\appendixpagename}{Appendix}
\begin{document}

\section{Introduction}
bla bla bla...

\begin{equation}
u_t+au_x=0,
\end{equation}
\section{Formulation}

\begin{appendices}
\section{Lalala}
The advection eq is...
\begin{equation}
u_t+au_x=0,
\end{equation}

\end{appendices}

\end{document}