Calculus (3rd Edition)

Published by W. H. Freeman
ISBN 10: 1464125260
ISBN 13: 978-1-46412-526-3

Chapter 1 - Precalculus Review - 1.2 Linear and Quadratic Functions - Exercises - Page 19: 49

Answer

$x + \frac{1}{x} \ge 2$ (and $x\gt 0$)

Work Step by Step

We know that $x^2 \ge 0$ for any real number $x$. Whenever $x>0$, then we can write: $(\sqrt{x} - \frac{1}{\sqrt{x}})^2 \ge 0$ Thus $x+\frac{1}{x} -2 \sqrt{x} \times \frac{1}{\sqrt{x}} = x + \frac{1}{x} -2 \ge 0$. Hence, $x + \frac{1}{x} \ge 2$ (and $x\gt 0$)
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