Chapter 2: Q4SE (page 93)
Suppose \({A^n} = {\bf{0}}\) for some \({\bf{n}} > {\bf{1}}\). Find an inverse for \(I - A\).
Short Answer
The inverse of \(I - A\) is \(I + A + {A^2} + ... + {A^{n - 1}}\).
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Chapter 2: Q4SE (page 93)
Suppose \({A^n} = {\bf{0}}\) for some \({\bf{n}} > {\bf{1}}\). Find an inverse for \(I - A\).
The inverse of \(I - A\) is \(I + A + {A^2} + ... + {A^{n - 1}}\).
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Prove the Theorem 3(d) i.e., \({\left( {AB} \right)^T} = {B^T}{A^T}\).
Suppose the third column of Bis the sum of the first two columns. What can you say about the third column of AB? Why?
Use matrix algebra to show that if A is invertible and D satisfies \(AD = I\) then \(D = {A^{ - {\bf{1}}}}\).
Solve the equation \(AB = BC\) for A, assuming that A, B, and C are square and Bis invertible.
Let \(A = \left( {\begin{aligned}{*{20}{c}}{\bf{2}}&{\bf{5}}\\{ - {\bf{3}}}&{\bf{1}}\end{aligned}} \right)\) and \(B = \left( {\begin{aligned}{*{20}{c}}{\bf{4}}&{ - {\bf{5}}}\\{\bf{3}}&k\end{aligned}} \right)\). What value(s) of \(k\), if any will make \(AB = BA\)?
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