MathDB
abcabc, d00d, radicals and integers - 1997 Romania NMO VII p1

Source:

August 13, 2024
number theoryInteger

Problem Statement

Let n1=abcabcn_1 = \overline{abcabc} and n2=d00dn_2= \overline{d00d} be numbers represented in the decimal system, with a0a\ne 0 and d0d \ne 0.
a) Prove that n1\sqrt{n_1} cannot be an integer. b) Find all positive integers n1n_1 and n2n_2 such that n1+n2\sqrt{n_1+n_2} is an integer number. c) From all the pairs (n1,n2)(n_1,n_2) such that n1n2\sqrt{n_1 n_2} is an integer find those for which n1n2\sqrt{n_1 n_2} has the greatest possible value