MathDB

2 + 2\sqrt{1 + 28n^2} is an integer, then it is the square of an integer

Source: 2005 Bosnia & Herzegovina JBMO TST p2

May 27, 2020

Perfect SquareIntegernumber theory

Problem Statement

Let n be a positive integer. Prove the following statement: ”If

2 + 2\sqrt{1 + 28n^2}

is an integer, then it is the square of an integer.”