Summary: Use this \LaTeX notation. The others are tested below.
This is inline $latex\Latex$ notation. $latex\vec{F}=m\vec{a}$.
This is new line notation: \LaTeX
\vec{F} = m\vec{a} .
Below is a “shortcode” block using $latex:
\vec{x}
Shortcode using the latex block:
\LaTeX\quad\vec{x}
HTML:
i\hbar\frac{\partial}{\partial t}\left|\Psi(t)\right> =H\left|\Psi(t)\right>If all works right, hopefully the equation \vec{x} = a^2 + b^2 creates inline latex.