Elementary Linear Algebra 7th Edition

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

Chapter 2 - Matrices - 2.3 The Inverse of a Matrix - 2.3 Exercises - Page 73: 69

Answer

See the proof below.

Work Step by Step

Since $A^{2}=A$, then $|A^{2}|=|A| |A|=|A|$ and thus $(I-2A)(I-2A)=I^{2}-2IA-2AI+4A^{2}=I-2A-2A+4A=I-4A+4A=I$ Therefore, $(I-2A)=(I-2A)^{-1}$
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