Go to https://www.codecogs.com/latex/eqneditor.php
Edit the equation as needed
Go to the bottom of the page and choose "URL Encoded"
Add URL to markdown page as an external image:
![equation](https://latex.codecogs.com/svg.latex?dx_i%20%3D%20x_i%20-%20%5Cbar%7Bx%7D)
IMPORTANT: the format was changed from png.latex
to svg.latex
for better resolution