Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 5 - Section 5.3 - Greatest Common Factors and Factoring by Grouping - Exercise Set - Page 349: 110

Answer

$\{(\frac{20}{11},-\frac{14}{11})\}$.

Work Step by Step

The given system of equations is $\left\{\begin{matrix} 3x& -2y&=&8\\ 2x& -5y & =&10 \end{matrix}\right.$ Determinant $D$ consists of the $x$ and $y$ coefficients. $D=\begin{vmatrix} 3& -2 \\ 2& -5 \end{vmatrix}=(3)(-5)-(2)(-2)=-15+4=-11$ For determinant $D_x$ replace the $x−$ coefficients with the constants. $D_x=\begin{vmatrix} 8& -2 \\ 10& -5 \end{vmatrix}=(8)(-5)-(10)(-2)=-40+20=-20$ For determinant $D_y$ replace the $y−$ coefficients with the constants. $D_y=\begin{vmatrix} 3& 8 \\ 2& 10 \end{vmatrix}=(3)(10)-(2)(8)=30-16=14$ By using Cramer's rule we have. $x=\frac{D_x}{D}=\frac{-20}{-11}=\frac{20}{11}$ and $y=\frac{D_y}{D}=\frac{14}{-11}=-\frac{14}{11}$ Hence, the solution set is $\{(x,y)\} =\{(\frac{20}{11},-\frac{14}{11})\}$.
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