Linear Algebra and Its Applications (5th Edition)

Published by Pearson
ISBN 10: 032198238X
ISBN 13: 978-0-32198-238-4

Chapter 3 - Determinants - 3.1 Exercises - Page 169: 3

Answer

$0$

Work Step by Step

Expansion across first row: $\begin{align} \det A & = 2\begin{vmatrix}1&2\\3&-1\end{vmatrix}+2\begin{vmatrix}3&2\\1&-1\end{vmatrix}+3\begin{vmatrix}3&1\\1&3\end{vmatrix}\\ & = 2(-1-6)+2(-3-2)+3(9-1)\\ & = -14-10+24=0 \end{align}$ Expansion down second column: $\begin{align} \det A & = 2\begin{vmatrix}3&2\\1&-1\end{vmatrix}+1\begin{vmatrix}2&3\\1&-1\end{vmatrix}-3\begin{vmatrix}2&3\\3&2\end{vmatrix}\\ & = 2(-3-2)+1(-2-3)-3(4-9)\\ & = -10-5+15=0 \end{align}$
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