Big Ideas Math - Algebra 1, A Common Core Curriculum

Published by Big Ideas Learning LLC
ISBN 10: 978-1-60840-838-2
ISBN 13: 978-1-60840-838-2

Chapter 7 - Polynomial Equations and Factoring - 7.3 - Special Products of Polynomials - Exercises - Page 376: 47

Answer

$a = 3, b = 5$

Work Step by Step

We have to find a solution of the following system of inequalities: $$\begin{cases} a^2-b^2<(a-b)^2\\ (a-b)^2<(a+b)^2. \end{cases}$$ Let's rewrite the system using the difference of squares pattern: $$\begin{cases} (a-b)(a+b)&<(a-b)^2\\ (a-b)^2&<(a+b)^2. \end{cases}$$ Move terms on one side in each inequality: $$\begin{cases} (a-b)(a+b)-(a-b)^2&<0\\ (a-b)^2-(a+b)^2&<0. \end{cases}$$ Factor $a-b)$ in the first inequality and use the difference of squares pattern in the second: $$\begin{cases} (a-b)(a+b-a+b)&<0\\ (a-b-a-b)(a-b+a+b)&<0. \end{cases}$$ Simplify: $$\begin{cases} 2b(a-b)&<0\\ -4ab&<0. \end{cases}$$ Simplify more: $$\begin{cases} b(a-b)&<0\\ ab&>0. \end{cases}$$ We conclude the following: $$(a>0,b>0,ab).$$ For example: $$a=3,b=5.$$
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