Intermediate Algebra (12th Edition)

Published by Pearson
ISBN 10: 0321969359
ISBN 13: 978-0-32196-935-4

Chapter 8 - Section 8.1 - The Square Root Property and Completing the Square - 8.1 Exercises - Page 511: 9

Answer

$\left\{\dfrac{1}{2},4\right\}$

Work Step by Step

In the form $ax^2+bx+c=0,$ the given equation, $ 2x^2=9x-4 ,$ is equivalent to \begin{align*} 2x^2-9x+4=0 .\end{align*} Using the factoring of trinomials in the form $ax^2+bx+c,$ the equation above has $ac= 2(4)=8 $ and $b= -9 .$ The two numbers with a product of $c$ and a sum of $b$ are $\left\{ -1,-8 \right\}.$ Using these $2$ numbers to decompose the middle term of the trinomial expression above results to \begin{array}{l}\require{cancel} 2x^2-x-8x+4=0 .\end{array} Grouping the first and second terms and the third and fourth terms, the given expression is equivalent to \begin{array}{l}\require{cancel} (2x^2-x)-(8x-4)=0 .\end{array} Factoring the $GCF$ in each group results to \begin{array}{l}\require{cancel} x(2x-1)-4(2x-1)=0 .\end{array} Factoring the $GCF= (2x-1) $ of the entire expression above results to \begin{array}{l}\require{cancel} (2x-1)(x-4)=0 .\end{array} Equating each factor to zero (Zero Product Property) and solving for the variable, then \begin{array}{l|r} 2x-1=0 & x-4=0 \\ 2x=1 & x=4 \\\\ x=\dfrac{1}{2} \end{array} Hence, the solution set of the equation $ 2x^2=9x-4 $ is $\left\{\dfrac{1}{2},4\right\}$.
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