There was a discussion on Twitter today about a mistake calculus students make:

I pointed out that it’s only off by one character:

The first equation is simply wrong. The second is correct, but a gross violation of convention, using *x* as a constant and *e* as a variable.

It’s wrong by one letter another way.

$\frac{d}{dx}e^x=e\,e^{x-1} \{=e^x\}$

Very neat. Which Twitter feed originated the discussion?

Many thanks

Jeff

Jeff: this tweet