Q:

Negative resistance in Thevenin equivalent using elementary devices?

Is it possible to generate a negative resistance Thevenin equivalent using just resistances, ideal voltage sources, ideal current sources? I need a negative slope straight line I with respect to V. Ideal Diodes may be used as well.

A:

You can only generate negative resistance by using active devices and here is such example 
.The courtesy of this circuit goes to user Spehro Pefhany
Circuit Simulation Link 

