Chapter 6: Problem 7
Show that any \(3 \times 3\) matrix of the form \\[ \left(\begin{array}{lll} a & 1 & 0 \\ 0 & a & 1 \\ 0 & 0 & b \end{array}\right) \\] is defective.
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Chapter 6: Problem 7
Show that any \(3 \times 3\) matrix of the form \\[ \left(\begin{array}{lll} a & 1 & 0 \\ 0 & a & 1 \\ 0 & 0 & b \end{array}\right) \\] is defective.
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Let \(\lambda\) be an eigenvalue of an \(n \times n\) matrix \(A\) and let \(\mathbf{x}\) be an eigenvector belonging to \(\lambda .\) Show that \(e^{\lambda}\) is an eigenvalue of \(e^{A}\) and \(\mathbf{x}\) is an eigenvector of \(e^{A}\) belonging to \(e^{\lambda}\)
Let \(T\) be an upper triangular matrix with distinct diagonal entries (i.e., \(t_{i i} \neq t_{j j}\) whenever \(i \neq j\) ). Show that there is an upper triangular matrix \(R\) that diagonalizes \(T\)
It follows from Exercise 14 that, for a diagonalizable matrix, the number of nonzero eigenvalues (counted according to multiplicity) equals the rank of the matrix. Give an example of a defective matrix whose rank is not equal to the number of nonzero eigenvalues.
Let \(A\) be a singular \(n \times n\) matrix. Show that \(A^{T} A\) is positive semidefinite, but not positive definite.
The city of Mawtookit maintains a constant population of 300,000 people from year to year. A political science study estimated that there were 150,000 Independents, 90,000 Democrats, and 60,000 Republicans in the town. It was also estimated that each year 20 percent of the Independents become Democrats and 10 percent become Republicans. Similarly, 20 percent of the Democrats become Independents and 10 percent become Republicans, while 10 percent of the Republicans defect to the Democrats and 10 percent become Independents each year. Let \\[ \mathbf{x}=\left(\begin{array}{r} 150,000 \\ 90,000 \\ 60,000 \end{array}\right) \\] and let \(\mathbf{x}^{(1)}\) be a vector representing the number of people in each group after one year (a) Find a matrix \(A\) such that \(A \mathbf{x}=\mathbf{x}^{(1)}\) (b) Show that \(\lambda_{1}=1.0, \lambda_{2}=0.5,\) and \(\lambda_{3}=0.7\) are the eigenvalues of \(A,\) and factor \(A\) into a product \(X D X^{-1},\) where \(D\) is diagonal (c) Which group will dominate in the long run? Justify your answer by computing \(\lim _{n \rightarrow \infty} A^{n} \mathbf{x}\)
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