Two functions, x^2 and e^x are walking down the street. Off in the distance they see a differential operator walking towards them. e^x turns to x^2 and tells him: “You better get out of here! If that operator differentiates you a few times you’ll disappear, but he can differentiate me all he wants and I’ll stay the same.”
So x^2 runs off and e^x goes to greet the differential operator. “Hi, I’m e^x” he says. “What’s your name?”
The operator looks at him with a demonic grin and says: “d/dy”.
For those with non-mathematical backgrounds:
d(e^x)/dy = 0, so e^x will be differentiated into oblivion (as he warned x^2, but presuming it would be a d/dx differential operator: d(x^2)/dx = 2x, d(2x)/dx = 2, d(2)/dx = 0, d(0)/dy = 0, etc.) instead of staying d(e^x)/dx = e^x, etc.
PS: also d(x^2)/dy = 0, so x^2 was right for running off in either case.*
nice jokes…
^ this was even funnier than above two jokes.