If you want to enable your users to do something, such as create an account on your system, DO NOT MAKE IT IMPOSSIBLY HARD.
Case in point:
If algebra is too hard, just refresh and you’ll see something else.
Woah, better refresh.
You know what this does? It not only keeps out any bots, but turns a normal human into something else:
With a zillion other websites out there, are you sure yours is compelling enough or contains such rare information that people will jump the gorge to get to it?