College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 6 - Matrices and Determinants - Exercise Set 6.5 - Page 652: 34

Answer

$x=-1$ $y=3$ $z=2$

Work Step by Step

First we have to compute the determinants $D,D_x,D_y,D_z$: $D=\begin{vmatrix}2&2&3\\4&-1&1\\5&-2&6\end{vmatrix}=2(-6+2)-2(24-5)+3(-8+5)=-55$ $D_x=\begin{vmatrix}10&2&3\\-5&-1&1\\1&-2&6\end{vmatrix}=10(-6+2)-2(-30-1)+3(10+1)=55$ $D_y=\begin{vmatrix}2&10&3\\4&-5&1\\5&1&6\end{vmatrix}=2(-30-1)-10(24-5)+3(4+25)=-165$ $D_z=\begin{vmatrix}2&2&10\\4&-1&-5\\5&-2&1\end{vmatrix}=2(-1-10)-2(4+25)+10(-8+5)=-110$ We use Cramer's Rule to determine the solutions of the system: $x=\dfrac{D_x}{D}=\dfrac{55}{-55}=-1$ $y=\dfrac{D_y}{D}=\dfrac{-165}{-55}=3$ $z=\dfrac{D_z}{D}=\dfrac{-110}{-55}=2$ The solution is: $x=-1$ $y=3$ $z=2$
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