Represent any number with two factorials I was wondering if it is possible to represent any positive integer with x! - y! ? If not, is there any proof?

You didn't say that $x$ and $y$ have to be integers!
So, for any real $z$, since the factorial
can be written in terms of the gamma function
($x! = \Gamma(x+1)$),
and $\Gamma(x)$ is continuous
for $x > 0$,
any real number can be written as
the difference of two factorials.
It's always a requirements problem.
