Intermediate Algebra for College Students (7th Edition)

Published by Pearson
ISBN 10: 0-13417-894-7
ISBN 13: 978-0-13417-894-3

Chapter 3 - Section 3.5 - Determinants and Cramer’s Rule - Exercise Set - Page 240: 42

Answer

$-407$

Work Step by Step

The given determinant is $\begin{vmatrix} \begin{vmatrix} 5&0 \\ 4 & -3 \end{vmatrix}& \begin{vmatrix} -1&0 \\ 0 &-1 \end{vmatrix} \\ \begin{vmatrix} 7& -5\\ 4&6 \end{vmatrix} & \begin{vmatrix} 4 & 1\\ -3 &5 \end{vmatrix} \end{vmatrix}$ First we solve the inner determinant. $\Rightarrow \begin{vmatrix} 5 & 0 \\ 4&-3 \end{vmatrix}=(5)(-3)-(4)(0)=-15-0=-15$ $\Rightarrow \begin{vmatrix} -1 & 0 \\ 0&-1 \end{vmatrix}=(-1)(-1)-(0)(0)=1-0=1$ $\Rightarrow \begin{vmatrix} 7 & -5 \\ 4&6 \end{vmatrix}=(7)(6)-(4)(-5)=42+20=62$ $\Rightarrow \begin{vmatrix} 4 & 1 \\ -3&5 \end{vmatrix}=(4)(5)-(-3)(1)=20+3=23$ Substitute all values into the given determinant and solve. $\Rightarrow \begin{vmatrix} -15 & 1 \\ 62&23 \end{vmatrix}=(-15)(23)-(62)(1)=-345-62=-407$
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