# How to write a the formulation of a non-linear programming problem

I'm having a little bit of trouble with using enumerate and align.

I'm trying to get this:

1. Is it OK to use the environment align?
2. How would the correct syntax in Latex be for writing the text shown in the image?
• What does enumerate have to do here? – Bernard Jul 4 '18 at 23:01
• @Bernard I don't know. – Alex Pozo Jul 4 '18 at 23:06
• Do you think you really have to number the conditions which define $C$? – Bernard Jul 4 '18 at 23:15
• @Bernard I need to number the conditions which define $C$. – Alex Pozo Jul 4 '18 at 23:23

The equations are all centred, so you can gather them:

\documentclass{article}

\usepackage{amsmath}

\begin{document}

\begin{gather}
\min_{\mathbf{Z} \in C} F(\mathbf{Z}), \\
\intertext{where $\mathbf{Z} = (x_1, \dots, x_N, u_1, \dots, u_n)$, and}
\begin{array}{ r @{} l }
C = \{ \mathbf{Z} \mid {} & g_i(\mathbf{Z}) = 0,\ i \in 1, \dots, r \\[\jot]
& g_j(\mathbf{Z}) \leq 0,\ j \in r + 1, \dots, m \}
\end{array}
\end{gather}

\end{document}


Here are a possibility, using mathtools (needless to load amsmath in this case):

\documentclass[a4paper, 11pt, french]{article}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{babel}
\usepackage{mathtools}
\usepackage{amssymb}

\begin{document}

\begin{flalign}
& & & \min_{\mathbf{Z}\in C} F(\mathbf{Z}), & & \\
& \mathrlap{\begin{aligned}\text{où }\mathbf {Z} & = (x_1,\dots, x_N, u_1,\dots, u_n) \\
\text{et } C & =\{\mathbf {Z}\mid \begin{aligned}[t] g_i(\mathbf{Z}) & = 0,\: i \in 1,\dots, r\\
g_j(\mathbf{Z}) & \leqslant 0,\: j \in r + 1,\dots, m\}
\end{aligned}
\end{aligned}}
\end{flalign}

\end{document}