Abstract
This note shows that every positive solution to the following third order non-autonomous max-type difference equation
x(n+1) = max {A(n)/x(n), x(n-2) }, n is an element of N-0,
when (A(n))(n is an element of N0) is a three-periodic sequence of positive numbers, is periodic with period three. The same result was proved for the following min-type difference equation
x(n+1) = min {A(n)/x(n), x(n-2)}, n is an element of N-0. (C) 2009 Elsevier Inc. All rights reserved.