Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 6 - Algebra: Equations and Inequalities - 6.5 Quadratic Equations - Exercise Set 6.5 - Page 400: 58

Answer

the solution set is\[\left\{ -1\pm \sqrt{5} \right\}\].

Work Step by Step

The given equation can be written as \[{{x}^{2}}+2x-4=0\]. Compare the given equation with the equation\[a{{x}^{2}}+bx+c=0\]. Here,\[a=1,\,\,b=2,\text{ and }c=-1\] Now put these values in the quadratic formula: \[x=\frac{-b\pm \sqrt{{{b}^{2}}-4ac}}{2a}\] That is, \[\begin{align} & x=\frac{-2\pm \sqrt{{{\left( 2 \right)}^{2}}-4\times 1\times \left( -4 \right)}}{2\times 1} \\ & =\frac{-2\pm \sqrt{4+16}}{2} \\ & =\frac{-2\pm 2\sqrt{5}}{2} \\ & =-1\pm \sqrt{5} \end{align}\] Hence, the solution set is\[\left\{ -1\pm \sqrt{5} \right\}\].
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