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: 37

Answer

See below

Work Step by Step

Given $$ A=\left[ \begin{array}{cccc}{-2} & {0} & {1} & {6} \\ {-1} & {3} & {-1} & {-4} \\ {2} & {1} & {0} & {3} \\ {0} & {5} & {-4} & {-2}\end{array} \right]$$ since,if we have \begin{aligned}A =\left[\begin{array}{lll}{a_{11}} & {a_{12}} & {a_{13}} \\ {a_{21}} & {a_{22}} & {a_{23}} \\ {a_{31}} & {a_{32}} & {a_{33}}\\a_{41} & a_{42} & a_{43}\end{array}\right] \end{aligned} So, we get \begin{aligned} \operatorname{det}(A)&=\left|\begin{array}{cccc}{-2} & {0} & {1} & {6} \\ {-1} & {3} & {-1} & {-4} \\ {2} & {1} & {0} & {3} \\ {0} & {5} & {-4} & {-2}\end{array}\right|, \ \\ & \text{from fourth row, we obtain}\\ \operatorname{det}(A)&=-2\cdot\left|\begin{array}{ccc}{3} & {-1} & {-4} \\ {1} & {0} & {3} \\ {5} & {-4} & {-2}\end{array}\right|+1.\cdot\left|\begin{array}{ccc}{-1} & {3} & {-4} \\ {2} & {1} & {3} \\ {0} & {5} & {-2}\end{array}\right|-6\cdot\left|\begin{array}{ccc}{-1} & {3} & {-1} \\ {2} & {1} & {0} \\ {0} & {5} & {-4}\end{array}\right|\\ &=-2 \cdot(3.0 \cdot(-2) +(-1).3.5+(-4).1 \cdot (-4)-3. \cdot 3 \cdot (-4)-(-1) \cdot 1 \cdot (-2)-(-4) \cdot 0 \cdot 5)+1.(-1 \cdot 1 .(-2) +3.3.0+(-4).2.5-(-1).3.5-3.2.(-2)-(-1).1\cdot 0)-6.(-1.1.(-4)+3.0.0+(-1).2.5-(-1).0.5-3.2.(-4)-(-1).1.0)\\ & =-2.35+(-11)-6.18\\ &=-70-11-108\\ &=-189 \end{aligned}
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