Linear Algebra and Its Applications (5th Edition)

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

Chapter 3 - Determinants - Supplementary Exercises - Page 188: 5

Answer

-12

Work Step by Step

Let \[A=\left|\begin{array}{ccccc} 9&1&9&9&9\\ 9&0&9&9&2\\ 4&0&0&5&0\\ 9&0&3&9&0\\ 6&0&0&7&0\end{array}\right|\] Expanding determinant $A$ along 2nd column \[A=(-1)^{1+2} \left|\begin{array}{cccc} 9&9&9&2\\ 4&0&5&0\\ 9&3&9&0\\ 6&0&7&0\end{array}\right|\] \[A=(-1) \left|\begin{array}{cccc} 9&9&9&2\\ 4&0&5&0\\ 9&3&9&0\\ 6&0&7&0\end{array}\right|\] Again expanding along 4th column \[A=(-1)(-1)^{1+4}(2)\left|\begin{array}{ccc} 4&0&5\\ 9&3&9\\ 6&0&7\end{array}\right|\] \[A=(2)\left|\begin{array}{ccc} 4&0&5\\ 9&3&9\\ 6&0&7\end{array}\right|\] Again expanding along 2nd column \[A=2[3(28-30)]\] \[\Rightarrow A=-12\]
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