Watched the video. The first method is what is usually taught to kids whereas his favorite is basically the needless guessing that kids will do on their own after they inevitably forget the first method due to hardly ever needing it. The second and third don't justify themselves at all, although you could easily restate them in followable form like this:
Let so that ; then
If you can get the students comfortable with it, you could drop the substitution and just do
That might be easier to remember than the first method. Still it's important to know that you can just do
>>14299377, and that one is the most likely to be retained. Plus it works when the factors have non-integer coefficients.
