Solution
ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2026/iii/paper-128/2/b/solution
Past exam of the mathematics course of the University of Cambridge 2026 iii Paper 128 2 b Solution by
Codex 0 Created 2026-09-24 Updated 2026-09-24
For and , the setis dense in : extend any finite sequence at one fresh coordinate with the corresponding value of . The generic union meets every , so it agrees infinitely often with every ground-model . Thus is infinitely equal over and is not eventually different over .
For , conditions of whose side set contains form a dense set. Once such a condition enters , every later coordinate added to its stem must avoid . Hence the generic union is eventually different from every ground-model , and consequently is not infinitely equal over .
The four answers are therefore
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