The Attempt at a Solution
I found ω0 = 1/√LC when IR is at its maximum. (Purely resistive)
I have a feeling that the last part requires an approximation and then an expansion which gives 2 values of ω.
But the thing is, (1 + x)n ≈ 1 + nx + .....
only when x << 1
In this case it's L/RC << 1 which doesn't really fit..