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

\def\BibTeX{{\rm B\kern-.05em{\sc i\kern-.025em b}\kern-.08em
    \DeclareMathOperator*{\argmax}{argmax} % thin space, limits underneath in displays
           \[\argmax_{\forall i\in N} \big(\zeta_i\big) \triangleq \zeta{(i^+)}\]
             \[\argmin_{\forall i\in N} \big(\zeta_i\big) \triangleq \zeta{(i^-)}\]


This is my expected sample image. enter image description here

  • 1
    could you share as an image of the equation you would like to write?
    – scd
    Oct 9, 2020 at 12:16
  • 1
    Yes, I edited the question for your kind considerations. Oct 9, 2020 at 12:42

1 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^-).

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

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

enter image description here


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

  • 1
    I'd go for your answer but embedded in subequations. This would provide a "single" number (so to say) for both equations, which seems to be what the OP is asking for.
    – campa
    Oct 9, 2020 at 13:11
  • 1
    Unrelated: how comes that your code has no syntax highlighting?
    – campa
    Oct 9, 2020 at 13:13
  • @campa - Many thanks for the suggestion to use a single equation number. I will update my answer accordingly. About the absence of syntax highlighting: Please see tex.meta.stackexchange.com/q/8668/5001 and tex.meta.stackexchange.com/a/8671/5001. Specifically, I insert the meta directives <!-- language: lang-none --> right in front of both code chunks. :-)
    – Mico
    Oct 9, 2020 at 13:22
  • 1
    Thank you so much. It's working for me. Oct 14, 2020 at 11:04

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