Differentiability question

1. Apr 18, 2010

losin

I want to show x->abs(x) is not differentiable at 0

Some techniques in analysis are required.... how should i do?

2. Apr 18, 2010

Landau

Calculate left and right limit of the difference quotient. If the function were differentiable, these would coincide, but they don't.

3. Apr 19, 2010

g_edgar

More basically ... use the definition of derivative.

4. Apr 19, 2010

Landau

The definition is the limit of the difference quotient.