Problem is, the link leads to a site about TeX, not MathJax. This is not really fortunate, as they're not equivalent; a link like this or this would have been much more helpful here. (The reason why I used the word "misleading" is that it literally says "MathJax" help, yet the link leads to a TeX site.)
I suggest using a link to Meta Math SE. It contains a lot of examples, allows to invoke editing (to grab the relevant MathJax template). This is also the page that is right now used at Physics SE. I currently do not see, why we would want to create our own Meta post for that, as we don't have anything custom (as opposed to Chemistry SE).
- I would also have to check if there are not issues in modifying that for a Beta site.