College Algebra (11th Edition)

Published by Pearson
ISBN 10: 0321671791
ISBN 13: 978-0-32167-179-0

Chapter 4 - Test - Page 472: 3

Answer

$x=\dfrac{1}{2}$

Work Step by Step

$\bf{\text{Solution Outline:}}$ To solve the given equation, $ \left( \dfrac{1}{8} \right)^{2x-3}=16^{x+1} ,$ express both sides in the same base. Once the bases are the same, equate the exponents. Use the properties of equality to isolate the variable. $\bf{\text{Solution Details:}}$ Using exponents, the equation above is equivalent to \begin{array}{l}\require{cancel} \left( \dfrac{1}{2^3} \right)^{2x-3}=(2^4)^{x+1} .\end{array} Using the Negative Exponent Rule of the laws of exponents which states that $x^{-m}=\dfrac{1}{x^m}$ or $\dfrac{1}{x^{-m}}=x^m,$ the equation above is equivalent to \begin{array}{l}\require{cancel} \left( 2^{-3} \right)^{2x-3}=(2^4)^{x+1} .\end{array} Using the Power Rule of the laws of exponents which is given by $\left( x^m \right)^p=x^{mp},$ the equation above is equivalent to \begin{array}{l}\require{cancel} 2^{-3(2x-3)}=2^{4(x+1)} \\\\ 2^{-6x+9}=2^{4x+4} .\end{array} Since the bases are the same, then the exponents can be equated. Hence, \begin{array}{l}\require{cancel} -6x+9=4x+4 \\\\ -6x-4x=4-9 \\\\ -10x=-5 \\\\ x=\dfrac{-5}{-10} \\\\ x=\dfrac{1}{2} .\end{array}
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