alignequationsmath-mode
I am writing to assign numbers to my equations in an optimization problem. However, Latex keeps giving one number for the single problem. How can to write it?
My code is
\begin{equation}
\begin{aligned}
& \underset{\mathbf{x}}{\text{maximize}}
& & \sum_{m}^{M} \sum_{k}^{K} \sum_{n}^{N} R_{m,k,n}^{T,UL} x_{m,k,n} \\
& \text{subject to}
& & \sum_{m}^{M} \sum_{k}^{K} x_{m,k,n} \leq 1, \; \forall n. \\
& & & \sum_{n}^{N} x_{m,k,n} \leq 1, \; \forall m,k.
\end{aligned}
\end{equation}
Use the align environments from amsmath:
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
\text{maximize} &\null \sum_{j=1}^n p_j x_j \\
\text{subject to} &\null \sum_{j=1}^n w_j x_j \leq c, \\
&\null x_j \in \{0, 1\}, \quad j=1,\dots,n.
\end{align}
\end{document}
Another solution (and numbering) with the empheq package (which loads mathtools, which loads amsmath):
\documentclass{article}
\usepackage[a4paper,margin=2.5cm]{geometry} % set page parameters
\usepackage{amsfonts, % for \mathbb and \mathcal macros
empheq}%
\numberwithin{equation}{subsection}
\setcounter{section}{1}
\setcounter{subsection}{1}
\begin{document}
\begin{subequations}
\begin{empheq}[left={\mathbb{E}(X)=\displaystyle\int_{-\infty}^{\infty} x\,dF(x)=\empheqlbrace}]{alignat = 2}
& \sum_{x \in \mathcal{X}} xf_{X}(x) =\sum_{x \in \mathcal{X}} x\mathbb{P}(X=x)
&\qquad & \text{if $X$ is discrete}, \\
& \int_{-\infty}^{\infty} xf_{X}(x)\,dx
& &\text{if $X$ is continuous}. \end{empheq}
\end{subequations}
\begin{subequations}
\begin{empheq}[left={\mathbb{E}(X)=\displaystyle∫_{-∞}^{∞} x\,dF(x)=\empheqlbrace}]{flalign}
& ∑_{x ∈ \mathcal{X}} xf_{X}(x) =∑_{x ∈ \mathcal{X}} x\mathbb{P}(X=x)
& &\text{if $X$ is discrete},&\hspace{5em} & \\
& ∫_{-∞}^{∞} xf_{X}(x)\,dx
&& \text{if $X$ is continuous}. \end{empheq}
\end{subequations}
\end{document}
Best Answer
Here are two possible solutions. Note that I've reduced the number of alignment points relative to your original code. In the second solution, only the two constraint equations are aligned relative to each other.