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: 60

Answer

$(-2,1,0,3)$

Work Step by Step

Step 1. Establish the augmented matrix of the system and use the Gauss Eliminations method: $\begin{vmatrix} 1 & -3 & 2 & 1 & -2 \\1 & -2 & 0 & -2 & -10\\0 & 0 & 1 & 5 & 15 \\3 & 0 & 2 & 1 & -3 \end{vmatrix} \begin{array}(\\R_2-R_1\to R_2 \\.\\R_4-3R_1\to R_4\\ \end{array}$ Step 2. Do the operations given on the right side of the matrix. $\begin{vmatrix} 1 & -3 & 2 & 1 & -2 \\0 & 1 & -2 & -3 & -8\\0 & 0 & 1 & 5 & 15 \\0 & 9 & -4 & -2 & 3 \end{vmatrix} \begin{array}(\\. \\.\\R_4-9R_2\to R_4\\ \end{array}$ Step 3. Do the operations given on the right side of the matrix. $\begin{vmatrix} 1 & -3 & 2 & 1 & -2 \\0 & 1 & -2 & -3 & -8\\0 & 0 & 1 & 5 & 15 \\0 & 0 & 14 & 25 & 75 \end{vmatrix} \begin{array}(\\. \\.\\14R_3-R_4\to R_4\\ \end{array}$ Step 4. Do the operations given on the right side of the matrix. $\begin{vmatrix} 1 & -3 & 2 & 1 & -2 \\0 & 1 & -2 & -3 & -8\\0 & 0 & 1 & 5 & 15 \\0 & 0 & 0 & 45 & 135 \end{vmatrix} \begin{array}(\\. \\.\\.\\ \end{array}$ Step 5. The last row of step 4 gives $w=3$, back substitute the results to row 3 to get $z=0$, to row 2 to get $y=1$, to row 1 to get $x=-2$. Thus the solution is $(-2,1,0,3)$
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