Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 9 - Systems and Matrices - Chapter 9 Test Prep - Review Exercises - Page 956: 83

Answer

\[\left[ {\begin{array}{*{20}{c}} 3&{ - 1} \\ { - 5}&2 \end{array}} \right]\]

Work Step by Step

\[\begin{gathered} \left[ {\begin{array}{*{20}{c}} 2&1 \\ 5&3 \end{array}} \right] \hfill \\ {\text{Let a matrix A}} = \left[ {\begin{array}{*{20}{c}} a&b \\ c&d \end{array}} \right],{\text{ its inverse is: }}{{\text{A}}^{ - 1}} = \frac{1}{{ad - bc}}\left[ {\begin{array}{*{20}{c}} d&{ - b} \\ { - c}&a \end{array}} \right] \hfill \\ {\text{Then}} \hfill \\ {{\text{A}}^{ - 1}} = \frac{1}{{\left( 2 \right)\left( 3 \right) - \left( 1 \right)\left( 5 \right)}}\left[ {\begin{array}{*{20}{c}} 3&{ - 1} \\ { - 5}&2 \end{array}} \right] \hfill \\ {\text{Simplifying}} \hfill \\ {{\text{A}}^{ - 1}} = \frac{1}{{6 - 5}}\left[ {\begin{array}{*{20}{c}} 3&{ - 1} \\ { - 5}&2 \end{array}} \right] \hfill \\ {{\text{A}}^{ - 1}} = \left[ {\begin{array}{*{20}{c}} 3&{ - 1} \\ { - 5}&2 \end{array}} \right] \hfill \\ \end{gathered} \]
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