cannot get my formula render correctly

[redstoneleo]

The output of the following code

from markdown_it import MarkdownIt
from mdit_py_plugins.front_matter import front_matter_plugin
from mdit_py_plugins.footnote import footnote_plugin
from mdit_py_plugins.anchors import anchors_plugin
from mdit_py_plugins.texmath import  texmath_plugin
from mdit_py_plugins.dollarmath import  dollarmath_plugin

md = (
    MarkdownIt('gfm-like' ,{'breaks':True,'html':True})
    # .use(texmath_plugin,delimiters='brackets')
    # .use(dollarmath_plugin)
	.use(front_matter_plugin)
    .use(footnote_plugin)
    .use(anchors_plugin, permalink=True, max_level=4)
    
    .enable('table')
)
s4=r'''a rational number like $\begin{matrix}
L & \  = \{ x \mid x \in \mathbb{Q},x \leq 0\} \cup \left\{ x \mid x \in \mathbb{Q},x > 0,x^{2} < 2 \right\} \\
U & \  = \mathbb{Q} - L = \left\{ x \mid x \in \mathbb{Q},x > 0,x^{2} > 2 \right\} \\
\end{matrix}$ .
  2.  A fact between two Dedekind cuts(the density of $Q$ in $R$): For any pair of real numbers $\alpha$ and $\beta$, where $\alpha > \beta$, there can always be found a real, and even in particular a rational, number $r$ which lies between them, i.e. $\alpha > r > \beta$ (and, consequently, an infinite set of such rational numbers).
'''
html_text = md.render(s4)

print(html_text)

is embedded at https://jsbin.com/gasacoq/edit?html,output , but the first formula was not rendered well, so what's wrong ?