Algebra 1: Common Core (15th Edition)

Published by Prentice Hall
ISBN 10: 0133281140
ISBN 13: 978-0-13328-114-9

Chapter 9 - Quadratic Functions and Equations - 9-5 Completing the Square - Practice and Problem-Solving Exercises - Page 579: 26

Answer

$y=5,-1$

Work Step by Step

$2y^2-8y-10$ Rewrite the equation as: $y^2-4y=5$ Compare it with the standard form of quadratic equation $ax^2+bx+c$, we have $a=1, b=-4$ Therefore, $b^2=4ac$ $\implies$ $c=\dfrac{b^2}{4a}$ Thus, $c=\dfrac{b^2}{4a}=\dfrac{(-4)^2}{4}=4$ To complete the square, add $1$ on both sides. $y^2-4y+4=5+4$ $\implies (y-2)^2=9$ $\implies y-2=3$ and $\implies y-2=-3$ or, $y=5,-1$
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