Precalculus (6th Edition)

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

Chapter 9 - Systems and Matrices - 9.7 Properties of Matrices - 9.7 Exercises - Page 930: 76

Answer

$\begin{bmatrix} 10 &-30 \\ 45 & -35 \end{bmatrix}$

Work Step by Step

$A^2=AA\\=\begin{bmatrix} 4 & -2 \\ 3 & 1 \end{bmatrix} \begin{bmatrix} 4 & -2 \\ 3 & 1 \end{bmatrix} \\=\begin{bmatrix} (4)(4)-2(3) &(4)(-2)-2(1) \\(3)(4)+3 & (3)(-2)+1 \end{bmatrix}\\=\begin{bmatrix} 16-6 &-8-2 \\15 & -6+1 \end{bmatrix} \\=\begin{bmatrix} 10 &-10 \\15 & -5 \end{bmatrix}$ Now, $A^3=A^2A\\=\begin{bmatrix} 10 &-10 \\15 & -5 \end{bmatrix} \begin{bmatrix} 4 & -2 \\ 3 & 1 \end{bmatrix} \\=\begin{bmatrix} 40-30 &-20-10 \\60- 15 & -30-5 \end{bmatrix} \\=\begin{bmatrix} 10 &-30 \\ 45 & -35 \end{bmatrix}$
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