I AM eˣ
- May 4
- 2 min read
Van Quy Khuc
Hanoi, 27-03-2026
In mathematics, many people are familiar with the function y = eˣ. It is a very special function: its derivative is itself, (eˣ)’ = eˣ, and its integral is also itself (plus a constant), ∫eˣ dx = eˣ + C.
There is a story about a crowded residential block where families lived close together. The kids in the neighborhood play with each other every day, so everyone knows everyone else’s “street reputation.”
Among them is a boy who is the most famous in the area because he practices martial arts. He often shows off a few fierce moves to assert his dominance. Whenever he performs, the other kids will stare wide-eyed and open-mouthed—both impressed and a little afraid—treating him like a young master of the neighborhood.
One day, as he returns from playing outside, he sees a crowd gathering at the alley entrance. When he asks, he learns that some kids are fighting.
Hearing that, he immediately shouts boldly:
— Who’s causing trouble? Everyone, step aside!
Then he charges straight into the middle of the crowd, as if even a moment’s delay will make people forget that he knows martial arts.
Sure enough, when the kids see him, they quickly move aside, leaving a clear space in the center, both respectful and slightly anxious.
But strangely, one kid remains standing still—calm, expressionless, not trembling, and showing no intention of stepping back.
The martial arts boy hesitates for a moment, then shouts loudly to save face:
— Who are you, not even afraid? I’ll differentiate right now! I’ll integrate you too!
The other child replies softly, but clearly enough for everyone to hear:
— I’m eˣ.
Silence fell over the group.
And for the first time in his life, the martial arts boy realizes that there are opponents who remain unchanged no matter how much you “differentiate” them, and who stay just as they are even when you “integrate” them.
From then on, his reputation remains, but whenever he tries to scare someone, the neighborhood kids will giggle:
— Be careful… what if it’s eˣ again?
*Note: Adapted from a story by Professor Kingfisher
References
[1] Vuong, Q. H. (2025). Wild Wise Weird. https://books.google.com/books?&id=rq82EQAAQBAJ
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