The scripts allow's math formulas to be written anywhere within the HTML code. To start a formula you use either a dollar sign $ or you can use a slash and an open parentheses "/(". To end the inline math, you have another dollar sign or a back slash and a closing parentheses. Enclosing in double dollar signs put the math on its own line. Or you can use the backslash and a hard bracket "\[".

If you need to actually use a regular dollar sign in the text, then you need to 'escape' it so the page doesn't think its the start of math. In order to escape it you use a backslash before the dollar sign. "\\$"

Dollar sign before and after:

$y=mx+1$

Parenthesis:

\(y=mx+2\)

Double Dollar Signs:

$$y=mx+3$$

Hard Bracket:

\[y=mx+5\]

In a sentence:

When $a \ne 0$, there are two solutions to \(ax^2 + bx + c = 0\) and they are

$$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$