Markdown rendering fails at image insertion and mathematical input

[Yonggie]

Math failure:

Image failure:

[Yonggie]

For question 2, I have figured that I have to use /files/image_name.png to let the project find the right img_path.

Any help on question 1?

[rjzupkoii]

Per the Guide inline MathJax notation is $$, so it should be $$k$$.