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The special set

Source: Bangladesh Mathematical Olympiad 2020 Problem 9

February 19, 2022
set theoryalgebra

Problem Statement

Bristy wants to build a special set AA. She starts with A={0,42}A=\{0, 42\}. At any step, she can add an integer xx to the set AA if it is a root of a polynomial which uses the already existing integers in AA as coefficients. She keeps doing this, adding more and more numbers to AA. After she eventually runs out of numbers to add to AA, how many numbers will be in AA?