方法1 修改页面加载

在 header.php 处加入

<script type="text/javascript" async
  src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.7/MathJax.js?config=TeX-MML-AM_CHTML">
</script>

 <script type="text/x-mathjax-config">
      MathJax.Hub.Config({
      extensions: ["tex2jax.js"],
      jax: ["input/TeX", "output/HTML-CSS"],
      tex2jax: {
        inlineMath: [ ['$','$'], ["\\(","\\)"] ],
        displayMath: [ ['′,′',''], ["\\[","\\]"] ],
        processEscapes: true
      },
      "HTML-CSS": { availableFonts: ["TeX"] }
      });
</script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.7/MathJax.js?config=TeX-MML-AM_CHTML"></script>

方法2 加载插件

插件市场搜索 MathJax-LaTeX
勾选 force load