Algebra 1

Published by Prentice Hall
ISBN 10: 0133500403
ISBN 13: 978-0-13350-040-0

Chapter 9 - Quadratic Functions and Equations - 9-5 Completing the Square - Practice and Problem-Solving Exercises - Page 565: 41



Work Step by Step

$3r^2-27r=3$ or, $r^2-9r=1$ Compare it with the standard form of quadratic equation $ax^2+bx+c$, we have $a=1, b=-9$ To complete the square, add $\dfrac{81}{4}$ on both sides. $r^2-9r+\dfrac{81}{4}=1+\dfrac{81}{4}$ $\implies (r-\dfrac{9}{2})^2=\dfrac{85}{4}$ $\implies (r-4.5)^2=21.25$ $\implies (r-4.5)=4.61$ and $\implies (r-4.5)=-4.61$ or, $r=9.11,-0.11$
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