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: 73

Answer

No

Work Step by Step

No, it is not because the sum of the inverses of the two matrices is not invertible the reason in the following Since $A$ and $B$ are invertible matrices, then $A+B=AB^{-1}B+AA^{-1}B=A(B^{-1}+A^{-1})B$ and then $(A+B)^{-1}=(A(B^{-1}+A^{-1})B)^{-1}=((B^{-1}+A^{-1})B)^{-1}A^{-1}=B^{-1} (B^{-1}+A^{-1})^{-1} A^{-1}$ for example, if $A=I$ and $B=-I$ , then $A^{-1}=I$ and $B^{-1}=-I$ , thus $B^{-1}+A^{-1}=O$ , thus the matrix $B^{-1}+A^{-1}$ is singular and then the matrix $B^{-1}+A^{-1}$ is not invertible
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