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 - Chapter 7 Test - Page 484: 14

Answer

the solution of these linear equations will be \[x=6\], and \[y=-5\].

Work Step by Step

In the first equation, multiply with 3, and in the second equation multiply with \[-5\], and after that both the equations: \[\begin{align} & \left[ 5x+4y=10 \right]\times 3 \\ & \left[ 3x+5y=-7 \right]\times -5 \end{align}\] After multiplication, \[\begin{align} & 15x+12y=30 \\ & -15x-25y=35 \end{align}\] Add both equations, \[\begin{align} & \left( 15x-15x \right)+\left( 12y-25y \right)=\left( 30+35 \right) \\ & -13y=65 \\ & y=-5 \end{align}\] Now, back substitute the value of y in any one of the equations. \[\begin{align} & 5x+4y=10 \\ & 5x+4\times -5=10 \\ & 5x-20=10 \\ & 5x=30 \end{align}\] On solving,\[x=6\] Therefore, the solution of these linear equations will be \[x=6\], and \[y=-5\].
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