dx dt =ax+by dy dt =−x − y,
2. As the values of a and b are changed so that the point (a,b)
moves from one region to another, the type of the linear system
changes, that is, a bifurcation occurs. Which of these bifurcations
is important for the long-term behavior of solutions? Which of
these bifurcations corresponds to a dramatic change in the phase
plane or the x(t)and y(t)-graphs?