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 640: 46

Answer

$\left[\begin{array}{ll} 1/4 & 5/8\\ 1/2 & 3/4 \end{array}\right]$

Work Step by Step

If $A=\left[\begin{array}{ll} a & b\\ c & d \end{array}\right]$, then $A^{-1}=\displaystyle \frac{1}{ad-bc}\left[\begin{array}{ll} d & -b\\ -c & a \end{array}\right]$. ---------------------- $I-A=\left[\begin{array}{ll} 1 & 0\\ 0 & 1 \end{array}\right]-\left[\begin{array}{ll} 7 & -5\\ -4 & 3 \end{array}\right]=\left[\begin{array}{ll} -6 & 5\\ 4 & -2 \end{array}\right]$ $ad-bc=(-6)(-2)-5(4)=-8$ $(I-A)^{-1}=\displaystyle \frac{1}{-8}\left[\begin{array}{ll} -2 & -5\\ -4 & -6 \end{array}\right]=\displaystyle \left[\begin{array}{ll} 1/4 & 5/8\\ 1/2 & 3/4 \end{array}\right]$
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