\documentclass[11pt]{article}

\usepackage[sans]{myctex}


\title{思源黑体 + FiraGO}
\date{\today}

\begin{document}
\maketitle

test math font.

\[
G'=(V,E)
\]
\textbf{math!!! 粗的!}
$MATH$

\section{is this bold $MATH \Z$?}
\section{这是bold $\text{你好abc}\R$?}
\begin{theorem}[sbada]
    aaa
\end{theorem}

\begin{equation}
\begin{aligned}
\min&   &   \sum_x \delta_x&    &   &\\
s.t.&   &   (1-\delta_x - \delta_y) d^2(x,y)\leq \|v_x-v_y\|^2 &\leq (c^2+(\delta_x+\delta_y)f(k)) d^2(x,y) &   &\forall x,y\in X\\
    &   &   \delta_x\in [0,1], v_x&\in \R^p   &   &\forall x\in X
\end{aligned}
\end{equation}


\end{document}