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 - 3.4 Applications of Determinants - 3.4 Exercises - Page 136: 15

Answer

The statement is correct.

Work Step by Step

Since $A$ is invertible, then $ A^{-1} =1/|A| * adj A $ and $ (A^{-1})^{-1} =1/|A^{-1}| * adj A^{-1} $ and then $ A^{-1} = ( (A^{-1})^{-1})^{-1} =|A^{-1}| * (adj A^{-1})^{-1} $ We know that $|A^{-1}|=1/|A|$ and $ A^{-1} =1/|A| * adj A $ Therefore, $1/|A| * adj A =|A^{-1}| * (adj A^{-1})^{-1} =(1/|A|) * (adj A^{-1})^{-1} $ Thus $ adj A = (adj A^{-1})^{-1} $ and then $ (adj A)^{-1} = adj A^{-1} $
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.