Farrooh F. answered 06/05/22
Physics & Math Expert — AP, SAT, Olympiads, Advanced Courses
For a) note that since friction exists, the particle will eventually end up at a global minimum. This means, that the first derivative of the potential must equal zero and the second derivative be positive.
For b) write down the Lagrangian, and equations of motion from there. You would end up with natural frequency.