Thinking Mathematically (6th Edition)

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

Chapter 6 - Algebra: Equations and Inequalities - Chapter Summary, Review, and Test - Review Exercises - Page 405: 48

Answer

The solution set is \[\left\{ -4,8 \right\}\].

Work Step by Step

Step 1: Shift all nonzero terms to left sides and obtain zero on the other side. For this, subtract 32 from both sides to get \[{{x}^{2}}-4x-32=0\]. Step 2: Find the factor of the above equation: Consider the equation, \[{{x}^{2}}-4x-32=0\] Factorize it as follows: \[\begin{align} & {{x}^{2}}-4x-32=0 \\ & {{x}^{2}}-8x+4x-32=0 \\ & x\left( x-8 \right)+4\left( x-8 \right)=0 \\ & \left( x+4 \right)\left( x-8 \right)=0 \end{align}\] Step 3 and 4: Set each factor equal to zero and solve the resulting equation: From Step 2, \[\left( x+4 \right)\left( x-8 \right)=0\] By the zero product principal either \[\left( x+4 \right)=0\] or \[\left( x-8 \right)=0\]. Now \[\left( x+4 \right)=0\] implies that \[x=-4\] and \[\left( x-8 \right)=0\] implies that \[x=8\]. Step 5: Check the solution in the original equation: Check for\[x=-4\]. So consider, \[\begin{align} & {{x}^{2}}-4x-32=0 \\ & {{\left( -4 \right)}^{2}}-4\left( -4 \right)-32=0 \\ & 16+16-32=0 \\ & 0=0 \end{align}\] and, check for\[x=8\]. \[\begin{align} & {{x}^{2}}-4x-32=0 \\ & {{\left( 8 \right)}^{2}}-4\left( 8 \right)-32=0 \\ & 64-32-32=0 \\ & 0=0 \end{align}\]
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