Finite Math and Applied Calculus (6th Edition)

Published by Brooks Cole
ISBN 10: 1133607705
ISBN 13: 978-1-13360-770-0

Chapter 3 - Section 3.2 - Using Matrices to Solve Systems of Equations - Exercises - Page 204: 13

Answer

$ (\displaystyle \frac{10}{3},\frac{1}{3})$

Work Step by Step

Write the augmented matrix and, using row transformations arrive at the reduced row echelon form. ----------- Swap equations 1 and 2, remove decimals/fractions $\left[\begin{array}{lll} 0.1 & -0.1 & 0.3\\ 0.5 & 0.1 & 1.7\\ 1 & 1 & 11/3 \end{array}\right]\begin{array}{l} 10R_{1}.\\ 10R_{2}.\\ 3R_{3}. \end{array}$ $\left[\begin{array}{lll} 1 & - 1 & 3\\ 5 & 1 & 17\\ 3 & 3 & 11 \end{array}\right]\begin{array}{l} .\\ R_{2}-5R_{1}.\\ R_{3}-3R_{1}. \end{array}$ ... clears column $1,$ $\left[\begin{array}{lll} 1 & - 1 & 3\\ 0 & 6 & 2\\ 0 & 6 & 2 \end{array}\right]\begin{array}{l} .\\ .\\ R_{3}-R_{2}. \end{array}$ ... begin clearing column 2, $\left[\begin{array}{lll} 1 & - 1 & 3\\ 0 & 6 & 2\\ 0 & 0 & 0 \end{array}\right]\begin{array}{l} .\\ \frac{1}{6}R_{2}\\ . \end{array}$ ... leading 1 in row 2, $\left[\begin{array}{lll} 1 & - 1 & 3\\ 0 & 1 & 1/3\\ 0 & 0 & 0 \end{array}\right]\begin{array}{l} R_{1}+R_{2}.\\ .\\ . \end{array}$ ... clears column 2, $\left[\begin{array}{lll} 1 & 0 & 10/3\\ 0 & 1 & 1/3\\ 0 & 0 & 0 \end{array}\right]$ Last row: all zeros, so system is consistent. $x=10/3$ $y=1/3$ Solution: $ (\displaystyle \frac{10}{3},\frac{1}{3})$
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