You can use math AND spend a few lines explaining the non-trivial syntax. It wouldn't be hard to do in this case and since the article is clearly meant for a large audience, it's a mistake from the author to gloss over various relevant definitions.
What syntax did you consider non-trivial? The summation sign? The transpose superscript? The use of greek letters? (beta, rho here)
This is relatively basic notation for linear algebra, which I guess is the prerequisite for the reader.
That's fair. The example OP gave us was the use of the word "function." I'd be very impressed at a (useful) tutorial that never mentioned that word.