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(a + b)(a + c)(a + d)(b + c)(b + d)(c + d) =\overline{abcd}

Source: JBMO 2016 Shortlist N5

October 14, 2017
JBMOnumber theory

Problem Statement

Determine all four-digit numbers abcd\overline{abcd} such that (a+b)(a+c)(a+d)(b+c)(b+d)(c+d)=abcd(a + b)(a + c)(a + d)(b + c)(b + d)(c + d) =\overline{abcd} :