Did you know that there is a nice way to type math notation? Like \[ f(x) = 3x^2 + \ln(x)  \sqrt{x8} \in \mathscr{F}\big([8,\infty)\big) \] This is based on the document typesetting system LaTeX. To say it simply, LaTeX is a markup language, kinda like a programming language, that makes it easy to typeset mathematics. It is the standard tool professional mathematicians and other scientists use to draft papers and notes. It’s not hard to learn: here’s the syntax for that equation.
\begin{equation*}
f(x) = 3x^2 + \ln(x)  \sqrt{x8} \in \mathscr{F}\big([8,\infty)\big)
\end{equation*}
Getting started with LaTeX, I’d advise you to use Overleaf. The website Overleaf is designed to allow folks to collaborate on documents written with LaTeX, kinda like how Google Docs works with typical documents. I’ve written a small annotated LaTeX file in Overleaf that you can copy to get started. After logging into Overleaf you can click Copy Project under the Menu in the topleft of the page. For some guidance on learning the LaTeX language:

In terms of longform documentation, the Overleaf website has helpful guides to introduce you to the language. For a more robust resource, the LaTeX Wikibook is a reference I still often use.

The website Detexify is invaluable; it allows you to handdraw a mathematical symbol to find out the LaTeX command to create that symbol.

After you get used to the mechanics of LaTeX, you’ll need to develop some style and a workflow. Diomidis Spinellis’s LaTeX Advice provides a good start for this.
To set up an efficient workflow using LaTeX quickly (notetaking speed), see Gilles Castel’s tutorial and Elijan Mastnak’s guide.
A related bit of software that might interest you is TeX for Gmail. This is a chrome browser extension that allows you to type mathematics in an email using LaTeX’s syntax. Note that the default output/product for LaTeX is a PDF file. You can use either MathJax or KaTeX to render math on a webpage like I’ve done here.