Hello Mitch,
the problem comes from your second condition in Piecewise: Instead of x=3 it should read x==3. But you do not need this condition anyway, because the default will hold then. Alternatively you can define your function like so:
f[x_] := (x^2 - 9)/(x - 3)
f[3] = 0;
f[3.] = 0.0;
I do not know what your problem with pasting code here is - did you click the "Code Sample" icon before?
Regards -- Henrik
