Intermediate Algebra (12th Edition)

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

Chapter 9 - Chapter R-9 - Cumulative Review Exercises - Page 641: 11

Answer

Graph of $-4x+y\le5$

Work Step by Step

First, graph the equation $ -4x+y=5 $. To find points on the equation, $ -4x+y=5 $, substitute values of $x$ and solve for the corresponding value of $y$. That is, \begin{array}{l|r} \text{If }x=0: & \text{If }x=1: \\\\ -4(0)+y=5 & -4(1)+y=5 \\ 0+y=5 & -4+y=5 \\ y=5 & y=5+4 \\ & y=9 .\end{array} Thus, the points $ (0,5) $ and $ (1,9) $ are points on the line determined by the equation $ -4x+y=5 $. The graph of $-4x+y\le5$ is the area on and above or below the line $-4x+y=5$. To determine if it is above or below the line, use a test point, such as $(0,0)$. That is, \begin{align*}\require{cancel} -4(0)+0&\overset{?}\le5 \\ 0+0&\overset{?}\le5 \\ 0&\overset{\checkmark}\le5 .\end{align*} Since the substitution above ended with a true statement, then the graph is the area that includes the test point.
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