In article <9cSdnYGhH7CMpNrPnZ2dnUVZ_sCdnZ2d@megapath.net>, Hetware <firstname.lastname@example.org> wrote:
>So the answer is consensus among mathematicians holds that F(t) = (t^2 - >9)/(t - 3) is undefined at t=3?
> Perhaps what I should have said at the >outset is something along the lines of: on any given day, if I'm setting >up an equation in physics, and produce an expression such as F(t) = (t^2 >- 9)/(t - 3), I treat it as t+3, and do not expect any adverse >consequence from doing so.
Your simplification is not valid for t=3. If there is a real physical interpretation, perhaps you can derive the formula t+3 without going through the intermediate form (t^2-9)/(t-3). Or consider the special case t=3 to show that the result is indeed t+3 in that case too.
In fact, I would be interested to see a physical problem where you can't do that.