Algebra 2 (1st Edition)

Published by McDougal Littell
ISBN 10: 0618595414
ISBN 13: 978-0-61859-541-9

Chapter 4 Quadratic Functions and Factoring - 4.7 Complete the Square - 4.7 Exercises - Skill Practice - Page 288: 8


The solutions are $x=9+\sqrt{5}$ or $x=9-\sqrt{5}$

Work Step by Step

$ x^{2}-18x+81=5\qquad$ ...write left side as a binomial squared.($81=9^{2}$) $(x-9)^{2}=5\qquad$ ...take square roots of each side. $ x-9=\pm\sqrt{5}\qquad$ ...add $9$ to each side. $ x-9+9=\pm\sqrt{5}+9\qquad$ ...simplify. $x=9\pm\sqrt{5}$ $x=9+\sqrt{5}$ or $x=9-\sqrt{5}$
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