4. Formulate a differential system that exhibits a stable equilibrium and a bifurcation that destabilizes the equilibrium. (Any system is acceptable such as the van der Pol oscillator) 4-1. Show the stability around an equilibrium point analytically through the linearization and identify the bifurcation point. 4-2. Integrate the system numerically with the same step size before and after the bifurcation. 4-2-1. using the forward Euler method 4-2-2. using a higher-order Runge-Kutta method 4-3. Discuss the differences between the analytical and numerical stability of the same equilibrium point. (When is the stability different?)