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: 28

Answer

$(x,y) =\left(\frac{1}{5},\frac{3}{10}\right)$

Work Step by Step

The given system of equations is $\left\{\begin{matrix} 3x& -&2y&=&0\\ 5x& +&10y & =&4 \end{matrix}\right.$ Determinant $D$ consists of the $x$ and $y$ coefficients. $D=\begin{vmatrix} 3&-2 \\ 5& 10 \end{vmatrix}=(3)(10)-(5)(-2)=30+10=40$ For determinant $D_x$ replace the $x−$ coefficients with the constants. $D_x=\begin{vmatrix} 0&-2 \\ 4& 10 \end{vmatrix}=(0)(10)-(4)(-2)=0+8=8$ For determinant $D_y$ replace the $y−$ coefficients with the constants. $D_y=\begin{vmatrix} 3&0 \\ 5& 4 \end{vmatrix}=(3)(4)-(5)(0)=12-0=12$ By using Cramer's rule we have. $x=\dfrac{D_x}{D}=\dfrac{8}{40}=\dfrac{1}{5}$ and $y=\dfrac{D_y}{D}=\dfrac{12}{40}=\dfrac{3}{10}$ Hence, the solution set is $(x,y) =\left(\frac{1}{5},\frac{3}{10}\right)$.
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