Precalculus (6th Edition) Blitzer

Published by Pearson
ISBN 10: 0-13446-914-3
ISBN 13: 978-0-13446-914-0

Chapter 8 - Section 8.2 - Inconsistent and Dependent Systems and Their Applications - Exercise Set - Page 902: 3

Answer

The solution of the equations is, $\left\{ \left( -2z+2,\ 2z+\frac{1}{2},\ z \right) \right\}$.

Work Step by Step

The given system of equations can be written in matrix form as below: $\left[ \left. \begin{matrix} 5 & 8 & -6 \\ 3 & 4 & -2 \\ 1 & 2 & -2 \\ \end{matrix} \right|\begin{matrix} 14 \\ 8 \\ 3 \\ \end{matrix} \right]$ Solve this matrix as below: $\left[ \left. \begin{matrix} 5 & 8 & -6 \\ 0 & 2 & -4 \\ 1 & 2 & -2 \\ \end{matrix} \right|\begin{matrix} 14 \\ 1 \\ 3 \\ \end{matrix} \right]$ $ By,\ 3{{R}_{3}}-{{R}_{2}}\to {{R}_{2}}$ $\left[ \left. \begin{matrix} 5 & 8 & -6 \\ 0 & 2 & -4 \\ 0 & 2 & -4 \\ \end{matrix} \right|\begin{matrix} 14 \\ 1 \\ 1 \\ \end{matrix} \right]$ $ By,\ 5{{R}_{3}}-{{R}_{1}}\to {{R}_{3}}$ $\left[ \left. \begin{matrix} 5 & 8 & -6 \\ 0 & 2 & -4 \\ 0 & 0 & 0 \\ \end{matrix} \right|\begin{matrix} 14 \\ 1 \\ 0 \\ \end{matrix} \right]$ $ By,\ {{R}_{2}}-{{R}_{3}}\to {{R}_{3}}$ Convert the last row into equation form, $\begin{align} 0x+0y+0z=0 & \\ 0=0 & \\ \end{align}$ The last row does not add any information about the variables; therefore we will drop it. $\left[ \left. \begin{align} & \begin{matrix} 5 & 8 & -6 \\ \end{matrix} \\ & \begin{matrix} 0 & 2 & -4 \\ \end{matrix} \\ \end{align} \right|\begin{matrix} 14 \\ 1 \\ \end{matrix} \right]$ Convert this system into linear equations. $\begin{align} 5x+8y-6z=14 & \\ 2y-4z=1 & \\ \end{align}$ Write the values of x and y in terms of z and solve the equation, $\begin{align} & x=-2z+2 \\ & y=2z+\frac{1}{2} \\ \end{align}$ Hence the numbers satisfy the set of solutions $\left\{ \left( -2z+2,\ 2z+\frac{1}{2},\ z \right) \right\}$
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