Why are you saying the circuits are not linear? Which component in the circuit is a nonlinear component?I'm solving for V(T) I(T) etc. SO the circuits not linear, and supposition wont help (I have never been able to understand this intuitively.) I tried a solution that involved mesh current and some other trickery and got a second order differential equation for for the current in the right loop except it's not one that I know how to solve. Can anyone point me in the right direction?