将 case 标记分配给对齐环境

Question

您建议如何将案例标记分配给位于正确的，并且只在第一行或第一行附近？您可以看到我分配的标记与环境之间的间距太大，看起来不美观。

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{mathtools}
\makeatletter
\newcommand*{\rom}[1]{\expandafter\@slowromancap\romannumeral #1@}
\makeatother
\renewcommand{\baselinestretch}{1.5}
\linespread{1}
\begin{document}
\setlength{\parindent}{0ex}
\setlength{\jot}{14pt}

\rom 4. Let $f(\alpha) = 0$. Yet suppose otherwise, i.e. $f(\alpha) < 0$ or $f(\alpha) > 0$  

\vspace{7pt}
\romannumeral 1. 
\begin{align*}
\alpha - \delta < x < \alpha + \delta &\Rightarrow f(x) < 0 &&  (\text{\rom 1}) \\
\alpha < x_{0} < \alpha + \delta &\Rightarrow f(x') < 0
\end{align*}

\vspace{7pt}
But this contradicts $\alpha = \ \text{sup} \ A$, since $x' \in A$ but $x' > \alpha$

\vspace{7pt}
\romannumeral 2. 
\begin{align*}
\alpha - \delta < x < \alpha + \delta &\Rightarrow f(x) > 0  \\
\alpha - \delta < x_{0} < \alpha &\Rightarrow f(x') > 0 
\end{align*}
\end{document}

Answer 1

&&如果某个环境中产生的距离align对您来说太大，您可能可以使用alignat。

\documentclass{article}
\usepackage{amsmath}
\makeatletter
\newcommand*{\rom}[1]{\expandafter\@slowromancap\romannumeral #1@}
\makeatother
\begin{document}

\begin{alignat*}{2}
\alpha - \delta < x < \alpha + \delta & \Rightarrow f(x) < 0 & \quad & (\text{\rom 1}) \\
\alpha < x_{0} < \alpha + \delta      & \Rightarrow f(x') < 0
\end{alignat*}

\end{document}