Consider the 2-dimensional flow

$$\dot{x}=\mu\left(\frac{1}{3} x^{3}-x\right)+y, \quad \dot{y}=-x$$

where the parameter $\mu>0$. Using Lyapunov's approach, discuss the stability of the fixed point and its domain of attraction. Relevant definitions or theorems that you use should be stated carefully, but proofs are not required.