On: A visual proof that a^2 – b^2 = (a + b)(a – b)

[nuancebydefault]

Is that allowed? You will prove another equation. You cannot swap pi and e either.

[Ma8ee → nuancebydefault]

You are not swapping the values, you are swapping the names.

[nuancebydefault → Ma8ee]

I forgot the i for irony...

[kelnos → nuancebydefault]

pi and e aren't names; they're values. Of course you can't swap values.