How can I give argmin and argmin equation number?

Question

I want to give common equation number of both of them. How can I do that?

\documentclass{ieeeaccess}
\usepackage{cite}
\usepackage{amsmath,amssymb,amsfonts}
\usepackage{algorithmic}
\usepackage{graphicx}
\usepackage{textcomp}
\def\BibTeX{{\rm B\kern-.05em{\sc i\kern-.025em b}\kern-.08em
    T\kern-.1667em\lower.7ex\hbox{E}\kern-.125emX}}
    \DeclareMathOperator*{\argmax}{argmax} % thin space, limits underneath in displays
\DeclareMathOperator*{\argmin}{argmin}
\begin{document}
           \[\argmax_{\forall i\in N} \big(\zeta_i\big) \triangleq \zeta{(i^+)}\]
     and                     
             \[\argmin_{\forall i\in N} \big(\zeta_i\big) \triangleq \zeta{(i^-)}\]
\EOD

\end{document}

This is my expected sample image.

Answer 1

• I suggest you replace both instances of \[ with \begin{equation} and both instances of \] with \end{equation}.

• I would also omit all four instances of \big. Aside: Do you need the parentheses around \zeta_i? I.e., why not just write \argmax_{\forall i\in N} \zeta_i and \argmax_{\forall i\in N} \zeta_i?

• The macro \zeta does not take an argument. Hence, just write \zeta(i^+) and \zeta(i^-).

\begin{equation}
\argmax_{\forall i\in N} \zeta_i \triangleq \zeta(i^+)
\end{equation}
and
\begin{equation}
\argmin_{\forall i\in N} \zeta_i \triangleq \zeta(i^-)
\end{equation}

---

Addendum: The following solution incorporates @campa's suggestion to use a single, centered equation number for both equations.

\documentclass{ieeetran}
\usepackage{amsmath,amssymb}
\DeclareMathOperator*{\argmax}{arg\,max} 
\DeclareMathOperator*{\argmin}{arg\,min}

\begin{document}
\setcounter{equation}{14} % just for this example
\begin{equation}
\begin{split}
&\argmax_{\forall i\in N} \zeta_i \triangleq \zeta(i^+)\\
\text{and}\qquad& \\
&\argmin_{\forall i\in N} \zeta_i \triangleq \zeta(i^-)
\end{split}
\end{equation}

\end{document}