Differential Equations and Linear Algebra (4th Edition)

Published by Pearson
ISBN 10: 0-32196-467-5
ISBN 13: 978-0-32196-467-0

Chapter 3 - Determinants - 3.1 The Definition of the Determinant - Problems - Page 207: 33

Answer

\begin{array}{l}{\operatorname{det}(A)=\left|\begin{array}{ccc}{\sqrt{\pi}} & {e^{2}} & {e^{-1}} \\ {\sqrt{67}} & {1 / 30} & {2001} \\ {\pi} & {\pi^{2}} & {\pi^{3}}\end{array}\right| \approx 9601.88}\end{array}

Work Step by Step

Given $$ A=\left[ \begin{array}{ccc}{\sqrt{\pi}} & {e^{2}} & {e^{-1}} \\ {\sqrt{67}} & {1 / 30} & {2001} \\ {\pi} & {\pi^{2}} & {\pi^{3}}\end{array} \right]$$ Since, if we have$$A=\left[ \begin{array}{lll}{a_{11}} & {a_{12}} & {a_{13}} \\ {a_{21}} & {a_{22}} & {a_{23}} \\ {a_{31}} & {a_{32}} & {a_{33}}\end{array} \right]$$ we get \begin{aligned}\operatorname{det}(A)& =\left|\begin{array}{lll}{a_{11}} & {a_{12}} & {a_{13}} \\ {a_{21}} & {a_{22}} & {a_{23}} \\ {a_{31}} & {a_{32}} & {a_{33}}\end{array}\right| &=a_{11}( a_{22} a_{33}-a_{23} a_{32})-a_{12}( a_{21} a_{33}-a_{23} a_{31})+a_{13}( a_{21} a_{32}-a_{22} a_{31})\\ & =a_{11}( a_{22} a_{33}-a_{23} a_{32})-a_{12}( a_{21} a_{33}-a_{23} a_{31})+a_{13}( a_{21} a_{32}-a_{22} a_{31})\\ &=a_{11} a_{22} a_{33}+a_{12} a_{23} a_{31}+a_{13} a_{21} a_{32}-a_{11} a_{23} a_{32}-a_{12} a_{21} a_{33}-a_{13} a_{22} a_{31}\\ \end{aligned} Therefore, we get \begin{aligned} \operatorname{det}(A)&=\left|\begin{array}{ccc}{\sqrt{\pi}} & {e^{2}} & {e^{-1}} \\ {\sqrt{67}} & {1 / 30} & {2001} \\ {\pi} & {\pi^{2}} & {\pi^{3}}\end{array}\right|\\ & =\sqrt{\pi}(1 / 30)\left(\pi^{3}\right)+e^{2}(2001)(\pi)+e^{-1}(\sqrt{67})\left(\pi^{2}\right)-e^{-1}(1 / 30)(\pi)- \sqrt{\pi}(2001)\left(\pi^{2}\right)-e^{2}(\sqrt{67})\left(\pi^{3}\right)\\ & \approx 9601.88 \end{aligned}
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