Irrationally yours, e!

Alright, here's some fun (and charming!) mathematics for a peaceful Sunday afternoon:

Using the infinite series representation of e^x = 1 + x + x^2/2! + x^3/3! + ... + x^n/n! + ..., prove that e must be irrational.

(Hint: Go after 1/e. Trap this minion and he shall lead you to the Don!)

Note: No, e is not irrational by definition!

(Yes, of course, if you are stuck after trying for a while, by all means consult references (or reliable sites on the internet). I'm simply putting up math problems that I find charming 😊. These problems have made me appreciate how beautiful mathematics can be if you are a bit patient.)

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