Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 3 - Determinants - 3.4 Summary of Determinants - Problems - Page 241: 15

Answer

See below

Work Step by Step

According to Cramer's Rule for a $2\times 2$ system $Ax=b$ where $A=\begin{bmatrix} a_1 &b_1\\a_2&b_2 \end{bmatrix}$ and $b=\begin{bmatrix} c_1\\c_2 \end{bmatrix}$ we have $x_1=\frac{\begin{vmatrix} c_1 &b_1\\c_2&b_2 \end{vmatrix}}{\begin{vmatrix} a_1 &b_1\\a_2&b_2 \end{vmatrix}}=\frac{\begin{vmatrix} 0 &8\\-3&4 \end{vmatrix}}{\begin{vmatrix} 2 &8\\ -2&4 \end{vmatrix}}=\frac{0+24}{8+16}=1$ and $x_2=\frac{\begin{vmatrix} a_1 &c_1\\a_2&c_2 \end{vmatrix}}{\begin{vmatrix} a_1 &b_1\\a_2&b_2 \end{vmatrix}}=\frac{\begin{vmatrix} 2 &0\\-2&3 \end{vmatrix}}{\begin{vmatrix} 2 &8\\ -2&4 \end{vmatrix}}=\frac{-6+0}{8+16}=\frac{1}{4}$
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