Elementary Linear Algebra 7th Edition

Published by Cengage Learning
ISBN 10: 1-13311-087-8
ISBN 13: 978-1-13311-087-3

Chapter 3 - Determinants - 3.3 Properties of Determinants - 3.3 Exercises - Page 125: 30

Answer

$$|A|=2, \quad \left|A^{-1}\right|=\frac{1}{2}.$$

Work Step by Step

Since $$A=\left[ \begin {array}{cccc} 0&1&0&3\\ 1&-2&-3&1 \\ 0&0&2&-2\\ 1&-2&-4&1 \end {array} \right] ,$$ then we can find the inverse as follwos $$A^{-1}=\left[ \begin {array}{cccc} 2&-3&\frac{7}{2}&4\\ 1&-3&\frac{3}{2}&3 \\ 0&1&0&-1\\ 0&1&-\frac{1}{2}&-1 \end {array} \right] . $$ One can see that $$|A|=2, \quad \left|A^{-1}\right|=\frac{1}{2}.$$ Hence, we verify that $$\left|A^{-1}\right|=\frac{1}{|A|}.$$
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