Chapter 3: Q26Q (page 165)
Compute the determinants of the elementary matrices given in Exercise 25-30.
26. \(\left[ {\begin{aligned}{*{20}{c}}0&0&1\\0&1&0\\1&0&0\end{aligned}} \right]\).
Short Answer
The determinant of the matrix is \( - 1\).
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Chapter 3: Q26Q (page 165)
Compute the determinants of the elementary matrices given in Exercise 25-30.
26. \(\left[ {\begin{aligned}{*{20}{c}}0&0&1\\0&1&0\\1&0&0\end{aligned}} \right]\).
The determinant of the matrix is \( - 1\).
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Use Exercise 25-28 to answer the questions in Exercises 31 ad 32. Give reasons for your answers.
32. What is the determinant of an elementary scaling matrix with k on the diagonal?
Question: 6. Use Cramer’s rule to compute the solution of the following system.
\(\begin{array}{c}{x_{\bf{1}}} + {\bf{3}}{x_{\bf{2}}} + \,{x_{\bf{3}}} = {\bf{4}}\\ - {x_{\bf{1}}} + \,\,\,\,\,\,\,\,\,\,{\bf{2}}{x_{\bf{3}}} = {\bf{2}}\\{\bf{3}}{x_{\bf{1}}} + \,{x_{\bf{2}}}\,\,\,\,\,\,\,\,\,\,\,\,\, = {\bf{2}}\end{array}\)
Compute the determinant in Exercise 8 using a cofactor expansion across the first row.
8. \(\left| {\begin{array}{*{20}{c}}{\bf{4}}&{\bf{1}}&{\bf{2}}\\{\bf{4}}&{\bf{0}}&{\bf{3}}\\{\bf{3}}&{ - {\bf{2}}}&{\bf{5}}\end{array}} \right|\)
Question: In Exercise 16, compute the adjugate of the given matrix, and then use Theorem 8 to give the inverse of the matrix.
16. \(\left( {\begin{array}{*{20}{c}}{\bf{1}}&{\bf{2}}&{\bf{4}}\\{\bf{0}}&{ - {\bf{3}}}&{\bf{1}}\\{\bf{0}}&{\bf{0}}&{ - {\bf{2}}}\end{array}} \right)\)
Find the determinant in Exercise 20, where \[\left| {\begin{array}{*{20}{c}}{\bf{a}}&{\bf{b}}&{\bf{c}}\\{\bf{d}}&{\bf{e}}&{\bf{f}}\\{\bf{g}}&{\bf{h}}&{\bf{i}}\end{array}} \right| = {\bf{7}}\].
20. \[\left| {\begin{array}{*{20}{c}}{\bf{a}}&{\bf{b}}&{\bf{c}}\\{{\bf{d}} + {\bf{3g}}}&{{\bf{e}} + {\bf{3h}}}&{{\bf{f}} + {\bf{3i}}}\\{\bf{g}}&{\bf{h}}&{\bf{i}}\end{array}} \right|\]
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