Is the Function x->|x| Differentiable at 0?

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

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

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Calculate left and right limit of the difference quotient. If the function were differentiable, these would coincide, but they don't.
 
More basically ... use the definition of derivative.
 
The definition is the limit of the difference quotient.
 

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