Chapter 12.4, Problem 6P

Definition: A topology on a set X is a collection T of subsets of X having the following properties. (1) Both the empty set and X itself are elements of T. (2) The union of an arbitrary collection of elements of T is an element of T. (3) The intersection of a finite number of elements of T is an element of T. A set X with a specified topology T is called a topological space. The subsets of X that are members of are called the open sets of the topological space.

Definition: A topology on a set X is a collection T of subsets of X having the following properties. (1) Both the empty set and X itself are elements of T. (2) The union of an arbitrary collection of elements of T is an element of T. (3) The intersection of a finite number of elements of T is an element of T. A set X with a specified topology T is called a topological space. The subsets of X that are members of are called the open sets of the topological space.

3) Let a1, a2, and a3 be arbitrary real numbers, and define an = 3an 13an-2 + An−3 for all integers n ≥ 4. Prove that an = 1 - - - - - 1 - - (n − 1)(n − 2)a3 − (n − 1)(n − 3)a2 + = (n − 2)(n − 3)aı for all integers n > 1.