Solution

ID: past-exam-of-the-mathematical-methods-i-course-of-the-university-of-oxford/2014-resit/13/i/solution

For a nonzero real solution use the Bernoulli power substitution . Dividing the differential equation by gives . The integrating factor yields
Direct substitution shows this formula also solves the equation at its zeros. Division temporarily discarded the additional solution . Since the real power is not locally Lipschitz at zero, the complete real solution family also permits waiting-time solutions of a sublinear Bernoulli equation: join a zero interval to a displayed branch at a root of . At a joining point the branch and its derivative are both zero, so the joined function satisfies the original equation. On each open nonzero interval every solution has the displayed form.

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