# multiple equations alignment

I want to write three equations in the \begin{align}\end{align}

\begin{aligned}
\min_{x \in \mathbb{R}} &f_i(x), & \qquad \left(i=1,\,2,\,\,\dots,\,M\right),\\
\text{sujeita a } &\phi_j(x)=0,&  \left(i=1,\,2,\,\,\dots,\,J\right),\\
&\psi_k(x)\leq 0,  & \left(i=1,\,2,\,\,\dots,\,K\right),
\end{aligned}
\end{align}


This is my output:

But I want that $f_i(x)$ be left aligned with $\phi_j(x)=0,$ and $\psi_k(x)\leq 0,$ Any suggestion? I will be very greatful.

• I don't think \min and f_i(x) should be aligned separately. – hesham Aug 21 '20 at 23:11
• Thank you for all the answers. All of you helped me a lot. I'm very grateful! – guiprado Aug 22 '20 at 18:51

You appear to have cropped out the equation number align would have provided - if you are looking for just one equation number, you can uncomment the commented lines here and comment out the alignat ones - or you can have the three equation numbers with alignat. (The excessive spacing in the code is for readability purposes here - no need for it in your actual document)

The extra braces around the min are to show it aligned with the text below - again, for illustrative purposes - I'd be inclined to agree with hesham that this may not be the best alignment for this display.

I have left the \left( and \right) on the first line to highlight the undesirable effect they have on the spacing. Please avoid them if possible.

\documentclass{article}
\usepackage{amsmath,amssymb}
\begin{document}
%\begin{align}
%\begin{aligned}
\begin{alignat}{3}
&{\min_{x \in \mathbb{R}}} &\quad &f_i(x),          &\quad &\left(i=1,\,2,\,\,\dots,\,M\right),
\\
&\text{sujeita a }       &\quad &\phi_j(x)=0,     &\quad &(i=1,\,2,\,\,\dots,\,J),
\\
&                        &      &\psi_k(x)\leq 0, &\quad &(i=1,\,2,\,\,\dots,\,K),
\end{alignat}
%\end{aligned}
%\end{align}
\end{document}


• Excuse me. What package do you have used, starting from \documentclass{..}? – Sebastiano Aug 22 '20 at 11:20
• Apologies - homebrewed documentclass - replaced now. Thanks. – Fintan Aug 22 '20 at 11:26
• No apologies :-)...don't worry. – Sebastiano Aug 22 '20 at 11:29

The tool of choise to have full control on the alignment columns spacing is alignat:

\documentclass{article}
\usepackage{amsmath, amssymb}

\begin{document}
\begin{alignat*}{3}
&\min_{x \in \mathbb{R}}&&f_i(x), & (i & =1,2,\ldots, M),\\
&\text{sujeita a }&&\phi_j(x)=0, & (j & =1,2,\ldots, J), \\
&&\quad&\psi_k(x)\leq 0, &\qquad (k & =1,2,\ldots K),
\end{alignat*}

\end{document}


Something of similar using flalign? I will use an array or alignat enviroments.

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amssymb}

\begin{document}
\begin{flalign}
&\min_{x \in \mathbb{R}}&&f_i(x),\quad  (i=1,2,\ldots, M),&&\notag\\
&\text{sujeita a }&&\phi_j(x)=0,\quad    (i=1,2,\ldots, J),&&\\
&&&\psi_k(x)\leq 0, \quad (i=1,2,\ldots K),&&\notag
\end{flalign}

\end{document}


Using alignat enviroment:

\documentclass[a4paper,12pt]{article}
\usepackage{amsmath,amssymb}

\begin{document}

\begin{alignat*}{2}
&\!\min_{x \in \mathbb{R}} &\quad& f_i(x), \quad  (i=1,2,\ldots, M),\\
&\text{sujeita a }& & \phi_j(x)=0, \quad (i=1,2,\ldots, J),\\
& & & \psi_k(x)\leq 0, \quad (i=1,2,\ldots K),
\end{alignat*}

\end{document}


• If you used alignedat within equation, you wouldn't need \notag. Also, on the first line, the last element should be aligned with the similar elements in the other two lines. – barbara beeton Aug 22 '20 at 0:01
• @barbarabeeton Approved! 😊 – Sebastiano Aug 22 '20 at 11:13

My preference would go to alignedat:

\documentclass{article}
\usepackage{amsmath,amssymb}

\begin{document}

\begin{alignedat}{3} &\!\min_{x \in \mathbb{R}} &\quad& f_i(x), &\qquad& (i=1,2,\dots,M),\\ &\text{sujeita a} &\quad& \phi_j(x)=0, &\qquad& (i=1,2,\dots,J),\\ & &\quad& \psi_k(x)\leq 0, &\qquad& (i=1,2,\dots,K), \end{alignedat}

\begin{alignedat}{3} &\!\min_{x \in \mathbb{R}} f_i(x), &\quad& &\qquad& (i=1,2,\dots,M),\\ &\text{sujeita a} &\quad& \phi_j(x)=0, &\qquad& (i=1,2,\dots,J),\\ & &\quad& \psi_k(x)\leq 0, &\qquad& (i=1,2,\dots,K), \end{alignedat}

\end{document}


In the second display, the objective function is not aligned with the bounds, which is more usual, I believe.