The synthetic division operator is looks like a floor symbol. But it is not exactly floor symbol. I tried a lot to find out the synthetic division operator using detexify. But I didn't find out it. How can I write synthetic division using MathJax?
I found this website: https://mathhelpboards.com/threads/synthetic-and-polynomial-long-division.10218/
It says that you can use this code:
\begin{array}{c|rrr}&1&2&1\\-1&&-1&-1\\\hline\\&1&1&0\\\end{array}
And I'm sure you can find a way to replace the numbers to fit your liking.