Intermediate Algebra for College Students (7th Edition)

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

Chapter 3 - Section 3.5 - Determinants and Cramer’s Rule - Exercise Set - Page 240: 22

Answer

$\{(1,-2)\}$.

Work Step by Step

Solve the given system using Cramer's Method. Rewrite the given system of equations in standard form: $\left\{\begin{matrix} 4x & +y & = &2 \\ 2x &-3y& = &8 \end{matrix}\right.$ The determinant $D$ consists of the $x-$ and $y-$ coefficients. We determine its value: $D=\begin{vmatrix} 4& 1\\ 2 & -3 \end{vmatrix}=(4)(-3)-(2)(1)=-12-2=-14$. For determinant $D_x$ replace the $x-$ coefficients with the constants. $D_x=\begin{vmatrix} 2& 1\\ 8 & -3 \end{vmatrix}=(2)(-3)-(8)(1)=-6-8=-14$. For determinant $D_y$ replace the $y-$ coefficients with the constants. $D_y=\begin{vmatrix} 4& 2\\ 2 & 8 \end{vmatrix}=(4)(8)-(2)(2)=32-4=28$. By using Cramer's rule we have. $x=\frac{D_x}{D}=\frac{-14}{-14}=1$ And $x=\frac{D_y}{D}=\frac{28}{-14}=-2$ Hence, the solution set is $\{(x,y)\}=\{(1,-2)\}$.
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