For each of the following exercises, sketch all the qualitatively different vector fields that occur as r is varied. Show that a saddle-node bifurcation occurs at a critical value of r, to be determined. Finally, sketch the bifurcation diagram of fixed points x versus r. 3.1.1 x=1+rx+x² 3.1.2 x r cosh x 3.1.3x+x-In (1+x) 3.1.4x=r+±x−x/(1+x)