# Homework Help: Interval Proof

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1. Oct 4, 2016

1. The problem statement, all variables and given/known data
Let $A_n = (n − 1, n + 1)$, for all natural numbers n. Find, with proof, $∪_{n≥1}A_n$

2. Relevant equations
What does that last statement mean? Union for n greater than or equal to one times the interval?

3. The attempt at a solution
I can't understand the question.

2. Oct 4, 2016

### Ray Vickson

It means $A_1 \cup A_2 \cup A_3 \cup \ldots$.