Sketch the phase plane of the system

$$\begin{aligned} &\dot{x}=y \\ &\dot{y}=-x+x^{2}-k y \end{aligned}$$

(i) for $k=0$ and (ii) for $k=1 / 10$. Include in your sketches any trajectories that are the separatrices of a saddle point. In case (ii) shade the domain of stability of the origin.