Precalculus (6th Edition) Blitzer

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

Chapter 8 - Section 8.5 - Determinants and Cramer's Rule - Exercise Set - Page 945: 11



Work Step by Step

As per Cramer's Rule , we have $x=\dfrac{D_x}{D}$ and $y=\dfrac{D_y}{D}$ The general formula to calculate the determinant of a $2 \times 2$ matrix which has 2 rows and 2 columns is $D=\begin{vmatrix}a&b\\c&d\end{vmatrix}=ad-bc$ Thus, $D=\begin{vmatrix}1&1\\1&-1\end{vmatrix}=-2$ and $D_x=\begin{vmatrix}7&1\\3&-1\end{vmatrix}=-10$ Also, $D_y=\begin{vmatrix}1&7\\1&3\end{vmatrix}=-4$ Now, $x=\dfrac{D_x}{D}=5$ and $y=\dfrac{D_y}{D}=2$ Hence, $(x,y)=(5,2)$
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