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 - 7.4 Linear Inequalities in Two Variables - Exercise Set 7.4 - Page 454: 41

Answer

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Work Step by Step

Let one variable be x and another variable be y. Sum of two variablesis at most 4.It gives \[x+y\le 4\] (1) The sum ofvariable y with 3 times the variable x does not exceed 6.It gives \[3x+y\le 6\] (2) Since both the inequalities in equation (1) and equation (2) are of the same sign, treat the equations as equality problem.It gives \[\begin{align} & 3x+y=6 \\ & x+y=4 \end{align}\] Subtract equation (1) from (2). \[\begin{align} & 2x=2 \\ & x=1 \end{align}\] Put the value of \[x=1\]in\[x+y=4\]. It gives \[\begin{align} & y+1=4 \\ & y=3 \end{align}\] Both the equations intersect at\[\left( 1,2 \right)\]. Now, we need to find the x-intercept and y-intercept of both the equations. \[3x+y=6\] For x-intercept,\[y=0\]. \[\begin{align} & 3x+y=6 \\ & 3x=6 \\ & x=2 \\ \end{align}\] So, the x-intercept of equation (1) is\[(2,0)\]. For y-intercept, \[x=0\]. \[\begin{align} & 3(0)+y=6 \\ & y=6 \\ \end{align}\] So, the y-intercept of the equation (1)is\[(0,6)\]. Again, for x-intercept, \[y=0\]. \[\begin{align} & x+y=4 \\ & x=4 \\ \end{align}\] So, the x-intercept of the equation (2) is\[(4,0)\]. For y-intercept, \[x=0\]. \[\begin{align} & x+y=4 \\ & y=4 \\ \end{align}\] So, the y-intercept of the equation (2) is\[(0,4)\]. The graph is given as
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