Just checking this now :\ I had to show that f is not differentiable at 0 so:

Potential Proof:

$\displaystyle |\frac{f(0+h) - f(0)}{h} - 0 | = |\frac{f(0+h) - f(0)}{h} |$

$\displaystyle =\fraq{{|f(h)|}} {{|h|}}$

$\displaystyle \le$ $\displaystyle \fraq{{h}} {{|h|}}$

$\displaystyle = 1$

I think I have made a big booboo and gone completely wrong, here is the whole of the question (its not an exam question, but a simple question from a group that our lecturer has given us to try and do over summer before anyone asks)

http://aimbot.fr/images/functions.png
PS: It is spose to show f(h) over the modulus of h and in the line below, h over modulus of h