Main Question or Discussion Point
explain it like im 12 years old.
OK, then you are prepared for something much better than a 12-year-old level explanation. There are a ton of good derivations online - find one, study it, come back with a more specific question.i do know upto multivariable.
OK, try this. It's a draft of an FAQ that I've been working on.i do know upto multivariable.