Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2025/iii/paper-130/3/a/solution

Let be the columns of the rational partition regular matrix , and clear denominators so that they are integer vectors. We use the P-adic columns lemma. For a large prime number , color each positive integer by a sufficiently long initial block of the unit part of its P-adic valuation, together with its valuation modulo the block length. Partition regularity supplies a monochromatic with
Group the indices according to the successive -adic orders of the . At the lowest order, division by the common power of and reduction modulo the chosen large power shows
Comparing the next nonzero blocks of base- digits shows successively that
For completeness, these congruences may be made exact by taking the digit block longer than every determinant and coordinate formed from the fixed columns: a nonzero such integer cannot be divisible by the resulting power of . There are only finitely many ordered partitions of , so passing through arbitrarily long blocks leaves one partition satisfying all the displayed identities. This is precisely the columns property.
Solved by gpt-5.6-sol high.

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