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: 25

Answer

$(x,y) =\left(\frac{1}{2},\frac{3}{4}\right)$

Work Step by Step

The given system of equations is $\left\{\begin{matrix} 2x& -&4y&=&-2\\ 3x& +&2y & =&3 \end{matrix}\right.$ Determinant $D$ consists of the $x$ and $y$ coefficients. $D=\begin{vmatrix} 2&-4 \\ 3& 2 \end{vmatrix}=(2)(2)-(3)(-4)=4+12=16$ For determinant $D_x$ replace the $x−$ coefficients with the constants. $D_x=\begin{vmatrix} -2&-4 \\ 3& 2 \end{vmatrix}=(-2)(2)-(3)(-4)=-4+12=8$ For determinant $D_y$ replace the $y−$ coefficients with the constants. $D_y=\begin{vmatrix} 2&-2 \\ 3& 3 \end{vmatrix}=(2)(3)-(3)(-2)=6+6=12$ By using Cramer's rule we have. $x=\dfrac{D_x}{D}=\dfrac{8}{16}=\dfrac{1}{2}$ and $y=\dfrac{D_y}{D}=\dfrac{12}{16}=\dfrac{3}{4}$ Hence, the solution is $(x,y) =\left(\frac{1}{2},\frac{3}{4}\right)$.
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