Thinking Mathematically (6th Edition)

Published by Pearson
ISBN 10: 0321867327
ISBN 13: 978-0-32186-732-2

Chapter 7 - Algebra: Graphs, Functions, and Linear Systems - 7.3 Systems of Linear Equations in Two Variables - Exercise Set 7.3 - Page 444: 7

Answer

See below:

Work Step by Step

The provided system of equations is: \[\begin{align} & 2x-3y=6 \\ & 4x+3y=12 \end{align}\] To solve it by graph method, plot the two lines in rectangular coordinate system. Use the following steps: Step 1: First graph the line \[2x-3y=6\]. Find x-intercept, set \[y=0\] in above equation. \[\begin{align} & 2x-3y=6 \\ & 2x-3\cdot 0=6 \\ & 2x=6 \\ & x=3 \end{align}\] Find y-intercept, set \[x=0\]in above equation. \[\begin{align} & 2x-3y=6 \\ & 2\cdot 0-3y=6 \\ & -3y=6 \\ & y=-2 \end{align}\] Plot the ordered pairs \[\left( 3,0 \right)\text{ and }\left( 0,-2 \right)\]. Step2: Draw a line passing through \[\left( 3,0 \right)\]and \[\left( 0,-2 \right)\]. Step3: Now graph the line \[4x+3y=12\]. Find x-intercept, set \[y=0\] in above equation. \[\begin{align} & 4x+3y=12 \\ & 4x+3\cdot 0=12 \\ & 4x=12 \\ & x=3 \end{align}\] Find y-intercept, set \[x=0\]in above equation. \[\begin{align} & 4x+3y=12 \\ & 4\cdot 0+3y=12 \\ & 3y=12 \\ & y=4 \end{align}\] Plot the ordered pairs \[\left( 3,0 \right)\text{ and }\left( 0,4 \right)\]. Step4: Draw a line that passes through \[\left( 3,0 \right)\]and \[\left( 0,4 \right)\]. Step5: From the graph, point of intersection is \[\left( 3,0 \right)\]. To ensure that the graph is accurate, check the point of intersection \[\left( 3,0 \right)\]in both equations. \[\begin{align} & 2x-3y=6 \\ & 2\cdot 3-3\cdot 0=6 \\ & 6-0=6 \\ & 6=6 \end{align}\] \[\begin{align} & 4x+3y=12 \\ & 4\cdot 3+3\cdot 0=12 \\ & 12+0=12 \\ & 12=12 \end{align}\] Coordinates of the point of intersection \[\left( 3,0 \right)\] that satisfies both the equations. Hence, the graph of the system of equations is correct.
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