To answer my own question. Just add this line to your markdown blog file <script src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML" type="text/javascript"></script>
---
title: "My blog"
tags: [something]
style: fill
color: dark
description: Another method o
---
<script src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML" type="text/javascript"></script>
$$ Y_i(t) = a_i + b_i t + c_i t + d_i t^3$$
To answer my own question. Just add this line to your markdown blog file
<script src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML" type="text/javascript"></script>