Solution

ID: past-exam-of-the-mathematics-course-of-the-year-2-of-the-natural-sciences-course-of-the-university-of-cambridge/2002/paper-1/8/b/solution

Choose the homogeneous solutions , which vanishes at , and , which vanishes at . Their Wronskian in the order is . For a source point , seek the Green's function as
It is continuous at ; otherwise its second distributional derivative would contain a derivative of the Dirac delta function, which the source does not contain. Integrating the differential equation across the source, using continuity and the leading coefficient one, gives the jump condition
Continuity and this derivative jump require
Solving with the Wronskian gives and . Therefore
The two values at are identical. The derivative jump is explicitly
Both endpoint values vanish and the differential expression is zero off the diagonal, completing the verification of the Green's function.

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