答案1
可能像这样吗?
\documentclass{article}
\usepackage{amsmath,amssymb}
\begin{document}
\begin{enumerate}
\item By definition $[x \sim y] \longleftrightarrow [6 \mid 4x+2y]
\longleftrightarrow [4x+2y \equiv 0 \pmod{6}]$
\begin{enumerate}
\item For reflexivity
\begin{gather*}
\forall x \in \mathbb{Z} :
4x+2x \equiv 6x \equiv 0\cdot x \equiv 0 \pmod{6} \\
\therefore [x \sim x]
\implies \forall x [x \in \mathbb{Z}] [x \sim x]
\end{gather*}
Therefore $\sim$ is reflexive.
\end{enumerate}
\end{enumerate}
\end{document}