Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

Published by Pearson
ISBN 10: 0-32193-104-1
ISBN 13: 978-0-32193-104-7

Chapter 10 - Systems of Equations and Inequalities - Section 10.2 Systems of Linear Equations: Matrices - 10.2 Assess Your Understanding - Page 749: 17

Answer

The system of equations is: $\left\{\begin{array}{llll} x & -3y & =-2\\ 2x & -5y & =5\\ \end{array}\right.$ Performing the indicated operations yield: $\left[\begin{array}{cc|c} {1}&{-3}&{-2}\\ {0}&{1}&{9}\end{array}\right]$

Work Step by Step

The standard form of a linear equation can be expressed as: $a_{i1}x_{1}+a_{i2}x_{2}+..........+a_{in}x_{n}=b_{i}$ where, the index $i$ indicates that it is the i-th equation of a system of equations. In order to write the augmented matrix $[A|B]$ of a system of equations in standard form, we must follow some important points: 1. To express a system in matrix form, we must extract the coefficients of the variables and constants. 2. Draw a vertical line to separate the coefficient entries from the constants (essentially replacing the equal signs). 3. The entries of the coefficient matrix $A=[a_{ij}]$ must be placed to the left of the lline. 4. The constants of the $B=[b_{i}]$ must be placed to the right of the line. The system of equations can be expressed as follows: $\left\{\begin{array}{llll} x & -3y & =-2\\ 2x & -5y & =5\\ \end{array}\right.$ We can write the system as an augmented matrix $[A|B]$ as follows: $[A|B]=\left[\begin{array}{rr|r} {1}&{-3}&{-2}\\ {2}&{-5}&{5}\end{array}\right]$ We perform the row operation as: $ R_{2}=-2r_{1}+r_{2}$ $=\left[\begin{array}{cc|c} {1} &{-3} &{-2}\\ {-2+2}&{6+(-5)}&{4+5}\end{array}\right]$ $=\left[\begin{array}{cc|c} {1}&{-3}&{-2}\\ {0}&{1}&{9}\end{array}\right]$
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