Algebra 1: Common Core (15th Edition)

Published by Prentice Hall
ISBN 10: 0133281140
ISBN 13: 978-0-13328-114-9

Chapter 6 - Systems of Equations and Inequalities - 6-1 Solving Systems by Graphing - Practice and Problem-Solving Exercises: 32

Answer

The student's error was not providing a wide enough graph to see the intersection point (-4,7)

Work Step by Step

Because the equations y=-x+3 and y=-2x-1 have different slopes, we know that they will eventually intersect at some point, but the student could not see this because the window chosen was not large enough. One method for solving, is to set both equations equal to each other: $-x+3 =-2x-1 \\ x+3=-1 \\ x=-4$ Plug the value of x back into the original equation of choosing to obtain the y-value: $y= -(-4)+3\\ y=7$ Now that we have our x and y value, we can identify our point of intersection as (-4,7)
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