Solution

ID: past-exam-of-the-mathematical-methods-i-course-of-the-university-of-oxford/2013/12/b/ii/solution

The logarithm requires for real-valued solutions. Put . Since , the equation becomes . For a nonzero branch, separation gives
Renaming the constant and restoring gives
Dividing by would omit the equilibrium , so the full solution set also includes . The nonzero branches are defined on connected intervals with and . A regular solution cannot switch from a nonzero branch to zero at an ordinary point, because the right-hand side is locally Lipschitz in there. These domain restrictions are part of the full real solution.

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