More derivatives because I am yet still lost on what I'm doing

Question

Let f(x) = x³-15x. Calculate the difference quotient

f (3+h) - f (3)

-----------------

h

h = 0.1 _______

h = 0.01 ______

h = -0.1 ______

h = -0.01 _______

If someone now told you that the derivative (slope of the tangent line to the graph) of f (x) at x = 3 was an integer, what would you expect it to be?

___________

Answer 1

The first part of the problem is simple substitution.

0.1 --> 12.91

0.01. --> 12.0901

-0.01. --> 11.91

-0.1. --> 11.11

By putting them in order, you can see that the numbers approach 12 as h approaches 0