Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 10 - Section 10.3 - Matrices and Systems of Linear Equations - 10.3 Exercises - Page 710: 50

Answer

$(-1,3,5)$

Work Step by Step

Write the augmented matrix and, using row transformations, arrive at the row-reduced echelon form. $\left[\begin{array}{llll} 2 & -3 & 5 & 14\\ 4 & -1 & -2 & -17\\ -1 & -1 & 1 & 3 \end{array}\right]\ \ \begin{array}{l} R_{1}\leftrightarrow R_{3}.\\ .\\ . \end{array}$ $\left[\begin{array}{llll} -1 & -1 & 1 & 3\\ 4 & -1 & -2 & -17\\ 2 & -3 & 5 & 14 \end{array}\right]\ \ \begin{array}{l} \times(-1).\\ +4R_{1}.\\ +2R_{1}. \end{array}$ $\left[\begin{array}{llll} 1 & 1 & -1 & -3\\ 0 & -5 & 2 & -5\\ 0 & -5 & 7 & 20 \end{array}\right]\ \ \begin{array}{l} .\\ .\\ -R_{2}. \end{array}$ $\left[\begin{array}{llll} 1 & 1 & -1 & -3\\ 0 & -5 & 2 & -5\\ 0 & 0 & 5 & 25 \end{array}\right]\ \ \begin{array}{l} .\\ .\\ \div 5. \end{array}$ $\left[\begin{array}{llll} 1 & 1 & -1 & -3\\ 0 & -5 & 2 & -5\\ 0 & 0 & 1 & 5 \end{array}\right] \ \ \begin{array}{l} +R_{3}.\\ -2R_{3}.\\ . \end{array}$ $\left[\begin{array}{llll} 1 & 1 & 0 & 2\\ 0 & -5 & 0 & -15\\ 0 & 0 & 1 & 5 \end{array}\right] \ \ \begin{array}{l} +\frac{1}{5}R_{2}.\\ \div(-5).\\ . \end{array}$ $\left[\begin{array}{llll} 1 & 0 & 0 & -1\\ 0 & 1 & 0 & 3\\ 0 & 0 & 1 & 5 \end{array}\right]$ Solution: $(-1,3,5)$
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