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: 12

Answer

$\left( 2,-1 \right)$

Work Step by Step

According to Cramer’s rule $x=\frac{{{D}_{x}}}{D}$, $y=\frac{{{D}_{y}}}{D}$ As $\begin{align} & D=\left| \begin{matrix} 2 & 1 \\ 1 & -1 \\ \end{matrix} \right| \\ & {{D}_{x}}=\left| \begin{matrix} 3 & 1 \\ 3 & -1 \\ \end{matrix} \right| \\ & {{D}_{y}}=\left| \begin{matrix} 2 & 3 \\ 1 & 3 \\ \end{matrix} \right| \end{align}$ Calculate the determinants. $\begin{align} & D=\left| \begin{matrix} 2 & 1 \\ 1 & -1 \\ \end{matrix} \right| \\ & =-2-1 \\ & =-3 \end{align}$ $\begin{align} & {{D}_{x}}=\left| \begin{matrix} 3 & 1 \\ 3 & -1 \\ \end{matrix} \right| \\ & =-3-3 \\ & =-6 \end{align}$ $\begin{align} & {{D}_{y}}=\left| \begin{matrix} 2 & 3 \\ 1 & 3 \\ \end{matrix} \right| \\ & =6-3 \\ & =3 \end{align}$ Substitute the given values $\begin{align} & x=\frac{{{D}_{x}}}{D} \\ & =\frac{-6}{-3} \\ & =2 \end{align}$ $\begin{align} & y=\frac{{{D}_{y}}}{D} \\ & =\frac{3}{-3} \\ & =-1 \end{align}$ Hence, $\left( x,y \right)=\left( 2,-1 \right)$
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