$f(0) = 65$, $f(20) = 60$, Possible to determine $f(x)$?

$f(0) = 65$, $f(20) = 60$, Possible to determine $f(x)$?

My question is pretty much what the title says. I have the following info:
$f(0) = 65$ and $f(20) = 60$. The curve is also exponential, it says.
Is it really possible to determine $f(x)$ from this information alone and
in that case, how is it done?
My literature only have very simple examples, and I can't find any lead in
there.