"I use this from time to time, but I think there's more steps than necessary in Ricalde's method.DiResta shows a simpler version in this video (around 6:15) (though he may oversimplify it for sake of the video)https://youtu.be/Y65tH4iMbg4"
"Very cool!This went around a while back, but I'm not sure who the original content creator is. Similar style...https://www.youtube.com/watch?v=RUNlLW6USSU"