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: 79

Answer

the solution set is\[\left\{ -\sqrt{6},\sqrt{6} \right\}\].

Work Step by Step

The given equation can be written as,\[2{{x}^{2}}-9x-3=9-9x\] Simplify this as follows: \[\begin{align} & 2{{x}^{2}}-9x-3-9+9x=0 \\ & 2{{x}^{2}}-12=0 \end{align}\] Compare the given equation with the equation,\[a{{x}^{2}}+bx+c=0\] Here,\[a=2,b=0\text{ and }c=-12\] Now, put these values in the quadratic formula: \[x=\frac{-b\pm \sqrt{{{b}^{2}}-4ac}}{2a}\] That is, \[\begin{align} & x=\frac{-0\pm \sqrt{{{0}^{2}}-4\times \left( 2 \right)\times \left( -12 \right)}}{2\times 2} \\ & =\frac{0\pm \sqrt{0+96}}{4} \\ & =\frac{0\pm 4\sqrt{6}}{4} \\ & =-\sqrt{6},\sqrt{6} \end{align}\] Hence, the solution set is\[\left\{ -\sqrt{6},\sqrt{6} \right\}\].
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