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 - 3.5 Chapter Review - Additional Problems - Page 244: 41

Answer

See below

Work Step by Step

Apply Cramer's Rule for a $3 \times 3$ system $Ax=b$ where $A=\begin{bmatrix} a_1 & b_1 & c_1\\a_2 & b_2 & c_2\\a_3 & b_3 & c_3 \end{bmatrix}$ and $b=\begin{bmatrix} d_1 \\ d_2 \\ d_3 \end{bmatrix}$ Obtain $x_1=\frac{\begin{vmatrix} d_1 &b_1 & c_1\\d_2 &b_2 &c_2\\d_3 &b_3 & c_3 \end{vmatrix}}{\begin{vmatrix} a_1 & b_1 & c_1\\a_2 & b_2 &c_2\\a_3 & b_3 & c_3 \end{vmatrix}}=\frac{\begin{vmatrix} 2 & -1&1\\ 0&5 & 3\\2 & -3 & 3 \end{vmatrix}}{\begin{vmatrix} 2 & -1 & 1\\ 4&5&3\\4 & -3&3 \end{vmatrix}}=\frac{160}{80}=2$ $x_2=\frac{\begin{vmatrix} a_1 & d_1 & c_1\\a_2 & d_2 &c_2 \\a_3 &d_3 & c_3 \end{vmatrix}}{\begin{vmatrix} a_1 & b_1 & c_1\\a_2 & b_2 &c_2\\a_3 & b_3 & c_3 \end{vmatrix}}=\frac{\begin{vmatrix} 4 & 0& 3\\ 2&2 & 1\\4 & 2 & 3 \end{vmatrix}}{\begin{vmatrix} 2 & -1 & 1\\ 4&5&3\\4 & -3&3 \end{vmatrix}}=\frac{4}{16}=\frac{1}{4}$ $x_3=\frac{\begin{vmatrix} a_1 &b_1 & d_1\\a_2 &b_2 & d_2\\ a_3 &b_3 & d_3 \end{vmatrix}}{\begin{vmatrix} a_1 & b_1 & c_1\\a_2 & b_2 &c_2\\a_3 & b_3 & c_3 \end{vmatrix}}=\frac{\begin{vmatrix} 2 & -1& 2\\ 4&5 & 0\\4 & -3 & 2 \end{vmatrix}}{\begin{vmatrix} 2 & -1 & 1\\ 4&5&3\\4 & -3&3 \end{vmatrix}}=-\frac{180}{80}=-\frac{9}{4}$
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