Plus a constant

Two mathematicians are in a bar. The first one says to the second that the
average person knows very little about basic mathematics. The second one
disagrees, and claims that most people can cope with a reasonable amount of
math.
The first mathematician goes off to the washroom, and in his absence the
second calls over the waitress. He tells her that in a few minutes, after his
friend has returned, he will call her over and ask her a question. All she has
to do is answer "one third x cubed."
She repeats "one third -- dex cue"?
He repeats "one third x cubed".
She asks, "one thir dex cuebd?"
"Yes, that's right," he says.
So she agrees, and goes off mumbling to herself, "one thir dex cuebd...".
The first guy returns and the second proposes a bet to prove his point, that
most people do know something about basic math. He says he will ask the blonde
waitress an integral, and the first laughingly agrees. The second man calls over
the waitress and asks "what is the integral of x squared?�
The waitress says "one third x cubed" and while walking away, turns back and
says over her shoulder "plus a constant!"