Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2017/ii/paper-4/31a/a/iii/solution

For , . The local attracting nonzero segments have or , again subject to ; the segment between the saddle-node and zero repels. The crossings at and one are saddle-node and transcritical. The quadratic-cubic flip criticality at the origin requires additional information: writing gives
It is supercritical if and subcritical if , with a degenerate flip if . The sign assumptions in case (iii) do not determine this criticality. The original “no further bifurcations in the region sketched” qualification is local; it does not remove this possible degeneracy or the additional crossings farther along fixed branches.

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