The derivative gives the rate of change of a function. From the graph, f'(3) = 3. This is a change of three units over one unit along the x-axis. you are going 3.1 - 3 = .1 units so you will have a change of .1[f'(3)].
Suppose you have a function f(x) and all you know is that f(3) = 25 and the graph of its derivative is:
http://img86.imageshack.us/img86/5896/sd...
Use linear approximation to estimate f(3.1):
any ideas?