RLC circuit with switch opening at t = 0

[ay.megaraptor]

1. The switch in the circuit shown in Figure has been closed for a long time
before t = 0 but opened at t = 0. Solve for i(t) for t ≥ 0.

*Hereby I attached the circuit diagram for the question above.

And this is where I got so far.
(6ohm+6ohm)=12ohm
alpha=R/2L
= 4 Neper.
But then I don't know how to solve for the rest.

 

[CEL]

We don't do homework for you. You must show some effort in order to get some help.
What were the current in the inductor and the voltage at the capacitor before the opening of the key. These are the initial conditions for your circuit.
Write the mesh equation for the circuit after the opening. You will have a second order differential equation.
Solve the differential equation and substitute the initial conditions.