MathDB
Composite sum

Source: 239 2012 S2

July 30, 2020
number theory

Problem Statement

Natural numbers a,b,c,da, b, c, d are given such that c>bc>b. Prove that if a+b+c+d=abāˆ’cda + b + c + d = ab-cd, then a+ca + c is a composite number.
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