Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 3 - Review Exercises - Page 249: 23

Answer

No.

Work Step by Step

The given system of equations is $\left\{\begin{matrix} x& +y &+z&=&0 \\ 2x& -3y & +z&=&5\\ 4x& +2y &+4z &=&3 \end{matrix}\right.$ The augmented matrix is $\Rightarrow \left[\begin{array}{ccc|c} 1 & 1 & 1& 0\\ 2 & -3 & 1& 5 \\ 4&2&4&3 \end{array}\right]$ Perform $R_2\rightarrow R_2-2\times R_1$ and $R_3\rightarrow R_3-4 R_1$. $\Rightarrow \left[\begin{array}{ccc|c} 1 & 1 & 1& 0\\ 2-2(1) & -3-2(1) & 1-2(1)& 5-2(0) \\ 4-4(1)&2-4(1)&4-4(1)&3-4(0) \end{array}\right]$ Simplify. $\Rightarrow \left[\begin{array}{ccc|c} 1 & 1 & 1& 0\\ 0 & -5 & -1& 5 \\ 0&-2&0&3 \end{array}\right]$ Perform $R_2\rightarrow \frac{R_2}{-5}$. $\Rightarrow \left[\begin{array}{ccc|c} 1 & 1 & 1& 0\\ 0/(-5) & -5/(-5) & -1/(-5)& 5/(-5) \\ 0&-2&0&3 \end{array}\right]$ Simplify. $\Rightarrow \left[\begin{array}{ccc|c} 1 & 1 & 1& 0\\ 0 & 1 & 1/5& -1 \\ 0&-2&0&3 \end{array}\right]$ Perform $R_1\rightarrow R_1- R_2$ and $R_3\rightarrow R_3+2 R_2$. $\Rightarrow \left[\begin{array}{ccc|c} 1-0 & 1-1 & 1-1/5& 0-(-1)\\ 0 & 1 & 1/5& -1 \\ 0+2(0)&-2+2(1)&0+2(1/5)&3+2(-1) \end{array}\right]$ Simplify. $\Rightarrow \left[\begin{array}{ccc|c} 1 & 0 & 4/5& 1\\ 0 & 1 & 1/5& -1 \\ 0&0&2/5&1 \end{array}\right]$ Perform $R_3\rightarrow R_3(5/2)$. $\Rightarrow \left[\begin{array}{ccc|c} 1 & 0 & 4/5& 1\\ 0 & 1 & 1/5& -1 \\ 0(5/2)&0(5/2)&2/5(5/2)&1(5/2) \end{array}\right]$ Simplify. $\Rightarrow \left[\begin{array}{ccc|c} 1 & 0 & 4/5& 1\\ 0 & 1 & 1/5& -1 \\ 0&0&1&5/2 \end{array}\right]$ Perform $R_1\rightarrow R_1-R_3(4/5)$ and $R_2\rightarrow R_2- R_3(1/5)$. $\Rightarrow \left[\begin{array}{ccc|c} 1-0(4/5) & 0-0(4/5) & 4/5-1(4/5)& 1-(5/2)(4/5)\\ 0-0(1/5) & 1-0(1/5) & 1/5-1(1/5)& -1-(5/2)(1/5) \\ 0&0&1&5/2 \end{array}\right]$ Simplify. $\Rightarrow \left[\begin{array}{ccc|c} 1 & 0 & 0& -1\\ 0 & 1 & 0& -3/2 \\ 0&0&1&5/2 \end{array}\right]$ Use back substitution to solve the linear system. $\Rightarrow x=-1$ and $\Rightarrow y=-3/2$. and $\Rightarrow z=5/2$. The solution set is $\{(x,y,z)\}=\{(-1,-3/2,5/2)\}$.
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