College Algebra (6th Edition)

Published by Pearson
ISBN 10: 0-32178-228-3
ISBN 13: 978-0-32178-228-1

Chapter 6 - Matrices and Determinants - Exercise Set 6.4 - Page 641: 86

Answer

The statement is false. To make it true, replace "$=A^{-1}B^{-1}$" with " $=B^{-1}A^{-1}$ ".

Work Step by Step

Since matrix multiplication is associative, $(AB)(B^{-1}A^{-1})=A(BB^{-1})A^{-1}$ $=AIA^{-1}=AA^{-1}=I$ and $(B^{-1}A^{-1})(AB)=B^{-1}(A^{-1}A)B$ $=B^{-1}IB=B^{-1}B=I$, the inverse of $(AB) $ is $(B^{-1}A^{-1})$, not $(A^{-1}B^{-1}).$ The statement is false. To make it true, replace "$=A^{-1}B^{-1}$" with " $=B^{-1}A^{-1}$ ".
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