Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 1 - Equations and Inequalities - 1.5 Applications and Modeling with Quadratic Equations - 1.5 Exercises - Page 129: 15

Answer

$\{9,11\}$ or $\{-11,-9\}$

Work Step by Step

Two consecutive odd integers, which can be represented by $x$ and $(x+2)$, are squared then added together to equal $202$ $(x)^2 + (x+2)^2=202$ $x^2 + x^2+4x+4=202$ $2x^2+4x+4=202$ $2x^2+4x-198=0$ Now, apply the quadratic formula: $x=\dfrac{-b\pm\sqrt{b^2-4ac}}{2a}$ $x=\dfrac{-4\pm\sqrt{4^2-4(2)(-198)}}{2(2)}$ $x=\dfrac{-4\pm\sqrt{16-8(-198)}}{4}$ $x=\dfrac{-4\pm\sqrt{16-8(-198)}}{4}$ $x=\dfrac{-4\pm\sqrt{16+1584}}{4}$ $x=\dfrac{-4\pm\sqrt{1600}}{4}$ $x=\dfrac{-4\pm40}{4}$ $x=\dfrac{-4+40}{4}$ or $x=\dfrac{-4-40}{4}$ $x=\dfrac{36}{4}$ or $x=\dfrac{-44}{4}$ $x=9$ or $x=11$ Now we check the answer: $9^2 +11^2 =202$ and $(-9)^2 +(-11)^2 =202$ $81 +121 =202$ So the solutions are $\{9,11\}$ or $\{-11,-9\}$
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