Algebra: A Combined Approach (4th Edition)

Published by Pearson
ISBN 10: 0321726391
ISBN 13: 978-0-32172-639-1

Chapter 11 - Section 11.3 - Integrated Review - Summary on Solving Quadratic Equations: 25


$x_{1}=6$ and $x_{2}=-11$

Work Step by Step

Given $x(x+5)=66 \longrightarrow x^2+5x-66=0$ $a= 1, \ b=5, \ c=-66$ Using the quadratic formula: $\dfrac{-b \pm \sqrt{b^2-4ac}}{2a}$ we have: $\dfrac{-5 \pm \sqrt{5^2-4 \times 1\times (-66)}}{2 \times 1} = \dfrac{-5 \pm \sqrt{25+264}}{2} = \dfrac{-5 \pm \sqrt{289}}{2} = \dfrac{-5 \pm 17}{2}$ Therefore the solutions are $x_{1}=\dfrac{-5 + 17}{2}=\dfrac{12}{2}=6$ and $x_{2} = \dfrac{-5 - 17}{2} = \dfrac{-22}{2}=-11$
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