How is the exponential function introduced in Math 100/180

I can't get the white spaces to work in the explanation - Bernhard do you know how?

Thanks for adding a few more words. I simplified your solution a little bit and added even more words. If you think it's good now, please flag accordingly.

Not sure why the white spaces didn't work. I usually use \text{foo} instead of textrm, maybe try that next time.

lol you really didn't like that solution...

okay I'll confirm.

also I couldn't get \text to work in math align mode...