答案1
例如(请观察 HoM 含义的变化。我假设这是您的意图):
\documentclass{article}
\usepackage{amsmath}
\DeclareMathOperator{\HoM}{Hom}
\begin{document}
The first bijection is induced...
\begin{equation}
\begin{aligned}
\pi(X,Y)&\to\HoM(X,Y)\\
[f]&\mapsto[RQf]
\end{aligned}
\end{equation}
if $X$ is cofibrant and $Y$ fibrant.
\end{document}