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:

This image will make you cry
Go ahead and register, I dare you

If algebra is too hard, just refresh and you’ll see something else.

Another scary image
I laugh at your feeble Calculus skills!

Woah, better refresh.

You can't escape the Maths
Make your time

You know what this does? It not only keeps out any bots, but turns a normal human into something else:

rageface
Apoplectic: overcome with anger; extremely indignant.

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?

https://www.youtube-nocookie.com/embed/P7vte1epVpE?rel=0