Thinking Mathematically (6th Edition)

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

Chapter 6 - Algebra: Equations and Inequalities - 6.2 Linear Equations in One Variable and Proportions - Exercise Set 6.2 - Page 363: 93

Answer

The value of \[{{x}^{2}}-x\]is \[2\].

Work Step by Step

The equation\[4\left( x-2 \right)+2=4x-2\left( 2-x \right)\]. Use the distributive property, \[a\left( b+c \right)=ab+ac\]. \[\begin{align} & 4x-8+2=4x-4+2x \\ & 4x-6=6x-4 \\ \end{align}\] Add \[4\]to both side, \[\begin{align} & 4x-6+4=6x-4+4 \\ & 4x-2=6x \\ \end{align}\] Subtract \[4x\] from both side, \[\begin{align} & 4x-4x-2=6x-4x \\ & -2=2x \end{align}\] Divided by 2 both side, \[\begin{align} & \frac{-2}{2}=\frac{2x}{2} \\ & -1=x \\ & x=-1 \\ \end{align}\] The solution set is \[\left\{ -1 \right\}\]. Check the proposed solution. Substitute \[-1\] for x in the original equation \[4\left( x-2 \right)+2=4x-2\left( 2-x \right)\]. \[\begin{align} & 4\left( -1-2 \right)+2=4\left( -1 \right)-2\left( 2+1 \right) \\ & 4\left( -3 \right)+2=-4-2\left( 3 \right) \\ & -12+2=-4-6 \\ & -10=-10 \end{align}\] This true statement \[-10=-10\] verifies that the solution set is \[\left\{ -1 \right\}\]. Now put \[x=-1\] in the expression \[{{x}^{2}}-x\]. \[\begin{align} & {{x}^{2}}-x={{\left( -1 \right)}^{2}}-\left( -1 \right) \\ & =1+1 \\ & =2 \end{align}\] Therefore, value of \[{{x}^{2}}-x\]is \[2\].
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