College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 5 - Summary, Review, and Test - Cumulative Review Exercises (Chapters 1-5) - Page 587: 20

Answer

$(2,8),\left(-\dfrac{1}{2},\dfrac{1}{2}\right)$

Work Step by Step

We are given the system: $\begin{cases} 3x-y=-2\\ 2x^2-y=0 \end{cases}$ We will use the substitution method. Solve Equation 1 for $y$ and substitute the expression of $y$ in Equation 2 to eliminate $y$ and determine $x$: $\begin{cases} y=3x+2\\ 2x^2-(3x+2)=0 \end{cases}$ $2x^2-3x-2=0$ $2x^2-4x+x-2=0$ $2x(x-2)+(x-2)=0$ $(x-2)(2x+1)=0$ $x-2=0\Rightarrow x_1=2$ $2x+1=0=0\Rightarrow x_2=-\dfrac{1}{2}$ Substitute each of the values of $x$ in the expression of $y$ to determine $y$: $y=3x+2$ $x_1=2\Rightarrow y_1=3(2)+2=8$ $x_2=-\dfrac{1}{2}\Rightarrow y_2=3\left(-\dfrac{1}{2}\right)+2=\dfrac{1}{2}$ The system's solutions are: $(2,8),\left(-\dfrac{1}{2},\dfrac{1}{2}\right)$
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