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: 19

Answer

\[\left\{ \left( -1,3 \right) \right\}\]

Work Step by Step

To find the solution of provided system of equation by substitution method and using the following steps: Step1: The first equation, \[2x-y=-5\], solve it for the y in terms of x. \[\begin{align} & 2x-y=-5 \\ & y=2x+5 \end{align}\] Step2: Substitute the value of \[y=2x+5\] into the other equation \[x+5y=14\]. The equation became in one variable x. Solve the equation for x: \[\begin{align} & x+5y=14 \\ & x+5\left( 2x+5 \right)=14 \\ & x+10x+25=14 \\ & 11x=14-25 \end{align}\] Simplify the above equation: \[\begin{align} & 11x=14-25 \\ & 11x=-11 \\ & x=-1 \end{align}\] Step3: Now, substitute the value of x obtained in step2 in \[y=2x+5\]: \[\begin{align} & y=2x+5 \\ & y=2\cdot \left( -1 \right)+5 \\ & y=-2+5 \\ & y=3 \\ \end{align}\] Step4: The value of x and y obtained in step2 and step3, is the solution of the provided system of equations. Hence \[\left\{ \left( -1,3 \right) \right\}\]is the required solution. Step5: Now, to verify that the obtained solution is correct, substitute the values of x and y in both equations. Put \[x=-1\text{ and }y=3\] \[\begin{align} & 2x-y=-5 \\ & 2\cdot \left( -1 \right)-3=-5 \\ & -2-3=-5 \\ & -5=-5 \end{align}\] \[\begin{align} & x+5y=14 \\ & -1+5\cdot 3=14 \\ & -1+15=14 \\ & 14=14 \end{align}\] Since, \[\left( -1,3 \right)\]satisfies both equations, the set \[\left( -1,3 \right)\]is the solution of the provided system of equations.
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