What is an example of real application of cubic equations? I didn't yet encounter to a case that need to be solved by cubic equations (degree three) !
May you give me some information about the branches of science or criterion deal with such nature ?

Voltage-current relationships of Thyristors ,Unijunction transistors and Tunnel Diodes  are cubic algebric expressions..........................
 V = a(0) +a(1)*I +a(2)*I^2 +a(3)*I^3......is a general Voltage (V) and Current (I) relationship  expression of these electronic devices.............Usually one of the roots is real and the other two are complex .
