Intermediate Algebra (6th Edition)

Published by Pearson
ISBN 10: 0321785045
ISBN 13: 978-0-32178-504-6

Chapter 4 - Review - Page 251: 51

Answer

$(-1,3,5)$

Work Step by Step

Multiplying the first equation by $ 3 $ and using the second equation, then \begin{cases} 3x-9y+6z=0 \\ 9y-z=22 .\end{cases} Adding the two equations and using the third equation, then \begin{cases} 3x+5z=22 \\ 5x+3z=10 .\end{cases} Multiplying the first equation above by $5$ and the second equation above by $3,$ then \begin{cases} 15x+25z=110 \\ 15x+9z=30 .\end{cases} Subtracting the two equations above results to \begin{array}{l}\require{cancel} 16z=80 \\ z=5 .\end{array} Substituting $z=5$ in the second equation, $9y-z=22,$ results to \begin{array}{l}\require{cancel} 9y-5=22 \\ 9y=22+5 \\ 9y=27 \\ y=\dfrac{27}{9} \\ y=3 .\end{array} Substituting $z=5$ in the third equation, $5x+3z=10,$ results to \begin{array}{l}\require{cancel} 5x+3(5)=10 \\ 5x+15=10 \\ 5x=10-15 \\ 5x=-5 \\ x=-\dfrac{5}{5} \\ x=-1 .\end{array} Hence, the solution is the point $ (-1,3,5) .$
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