Precalculus (10th Edition)

Published by Pearson
ISBN 10: 0-32197-907-9
ISBN 13: 978-0-32197-907-0

Chapter 11 - Systems of Equations and Inequalities - 11.3 Systems of Linear Equations: Determinants - 11.3 Assess Your Understanding - Page 742: 19

Answer

$(x,y) =(8,-4)$

Work Step by Step

Use zero for the missing variable. The given system of equations is $\left\{\begin{matrix} 3 x& +&0y&=&24\\ x& +&2y & =&0 \end{matrix}\right.$ Determinant $D$ consists of the $x$ and $y$ coefficients. $D=\begin{vmatrix} 3&0 \\ 1& 2 \end{vmatrix}=(3)(2)-(1)(0)=6-0=6$ For determinant $D_x$ replace the $x−$ coefficients with the constants. $D_x=\begin{vmatrix} 24&0 \\ 0& 2 \end{vmatrix}=(24)(2)-(0)(0)=48-0=48$ For determinant $D_y$ replace the $y−$ coefficients with the constants . $D_y=\begin{vmatrix} 3&24 \\ 1& 0 \end{vmatrix}=(3)(0)-(1)(24)=0-24=-24$ By using Cramer's rule we have. $x=\dfrac{D_x}{D}=\dfrac{48}{6}=8$ and $y=\dfrac{D_y}{D}=\dfrac{-24}{6}=-4$ Hence, the solution set is $(x,y) =(8,-4)$.
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