Problem finding the equations (theoretical electronics)

[B1ackID]

OK, so this is one of the problems I need to solve. I have made the schematics for the two cases and now I need to do the transition processes, meaning I have to make a system of equations, that will be used as a Matrix, so I can figure out the determinant (that's how we call them in our language, not sure if these are their names in English). From then on I can solve this, but I can't figure out the equations.
Can anyone help?

 

[gneill]

The picture of your transition schematic is truncated, so we cannot judge if it is correct. Also, you need to show some attempt at writing the mesh equations before we can see how to help you.