Question

Let f(x)=x^3-8(x). Calculate the difference quotient f(3+h)-f(3)/h
for
h=.1
h=.01
h=-0.1
h=-.1
If someone told you the derivative(slope of tangent line to the graph) of f(x) at x=3 was an integer, what would you expect it to be ?
(I'm confused in how to approach this problem, I know I can't just plug in the given h's into the diff.Quot. so would I plug in f(x) into h ? )