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 243: 5

Answer

-30

Work Step by Step

(a) $|A|=\begin{vmatrix} 0 & 0 & 0 & -2\\ 0 & 0 & -5 & 1\\ 0 & 1 & -4 & 1\\ -3 & -3 & -3 & -3 \end{vmatrix}=-2.(-5).1(-3)=-30$ b) Using elementary row operations: $|A|=\begin{vmatrix} 0 & 0 & 0 & -2\\ 0 & 0 & -5 & 1\\ 0 & 1 & -4 & 1\\ -3 & -3 & -3 & -3 \end{vmatrix} \approx \begin{vmatrix} -3 & -3 & -3 & -3\\ 0 & 0 & -5 & 1\\ 0 & 1 & -4 & 1\\ 0 & 0 & 0 & -2 \end{vmatrix} \approx \begin{vmatrix} -3 & -3 & -3 & -3\\ 0 & 1 & -4 & 1\\ 0 & 0 & -5 & 1\\ 0 & 0 & 0 & -2 \end{vmatrix}=-3.1.(-5).(-2)=-30$ c) Using the Cofactor Expansion Theorem $|A|=A_{11}C_{11}+A_{21}C_{21}+A_{23}C_{23}=-30$
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