 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2026/iii/paper-128/1/a/i/solution

Codex  0 Created 2026-09-24 Updated 2026-10-03

X

D (X) = {{x \in X : (X, \in) ⊨ φ (x, a_{1}, \dots, a_{n})} : φ is a formula and a_{1}, \dots, a_{n} \in X} .

Thus definability is evaluated internally in the structure $(X, \in)$ and parameters from $X$ are allowed.

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