 Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/ib/paper-2/9e/c/solution

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

R / I ≅ \prod_{i} R / (p_{i}^{e_{i}}) .

Thus a class is a unit exactly when its image modulo every $p_{i}$ is nonzero, equivalently when no $p_{i}$ divides a representative.

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