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					Originally Posted by Augi
					
				 
				Kebo, but I do know calculus and I know that d(|x|)/dx is not constant.  
 
d(|x|)/dx = { -1 , x<0 ; undefined , x=0 ; 1 , 0<x } 
 
If you need to see how that is done, just break |x| into three functions: y(x) = { -x , x<0 ; 0 , x=0 ; x , 0<x } . The derivative of y(0) can't occur because of the conflicting limits as you approach 0- and 0+ (You are in calculus right?). 
			
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 that's absolutely correct.  But according to sieger35's definition of an  affine function
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				If I'm not mistaken, an affine function is a linear form + a constant term.
			
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  the derivative must be constant.
kevin
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or at least it must be constant over the range of values in question