Now,
I haven't really said what G[x] is in terms of x. In order for me
to describe G[x] as a function of x, I would have to discuss calculus,
in particular, things called improper integrals. You'll probably learn
about these in senior high school mathematics courses. But the basic
idea behind the gamma function is this: We want a function which
generalizes the factorial function, so that property (B) is satisfied
for as many numbers x as possible. So in particular, we have: