Discrete Mathematics with Applications 4th Edition

Published by Cengage Learning
ISBN 10: 0-49539-132-8
ISBN 13: 978-0-49539-132-6

Chapter 7 - Functions - Exercise Set 7.4 - Page 440: 18

Answer

**Short Answer:** No, the average of two irrational numbers need not be irrational.

Work Step by Step

**Short Answer:** No, the average of two irrational numbers need not be irrational. For example, consider \[ \sqrt{2} \quad\text{and}\quad 2 - \sqrt{2}. \] Both are irrational, yet their average is \[ \frac{\sqrt{2} + (2 - \sqrt{2})}{2} \;=\; \frac{2}{2} \;=\; 1, \] which is rational. This provides a counterexample.
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