Past exam of the mathematics course of the University of Cambridge 2025 iii Paper 101 4 iii Solution Created 2026-09-24 Updated 2026-09-24
The polynomial ring is a two-dimensional unique factorization domain. Let be a prime ideal containing . Since , the prime is nonzero. If it were not maximal, it would have height one, so the height-one prime in a unique factorization domain would give for an irreducible polynomial . Then would divide both and , contrary to the hypothesis. Every prime ofis therefore maximal.
The Hilbert basis theorem makes Noetherian, and it has Krull dimension zero by the preceding paragraph. The Noetherian dimension-zero criterion for an Artinian ring now shows that