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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Given \\[ \mathbf{Y}=c_{1} e^{\lambda_{1} t} \mathbf{x}_{1}+c_{2} e^{\lambda_{2} t} \mathbf{x}_{2}+\cdots+c_{n} e^{\lambda_{n} t} \mathbf{x}_{n} \\] is the solution to the initial value problem: \\[ \mathbf{Y}^{\prime}=A \mathbf{Y}, \quad \mathbf{Y}(0)=\mathbf{Y}_{0} \\] (a) Show that \\[ \mathbf{Y}_{0}=c_{1} \mathbf{x}_{1}+c_{2} \mathbf{x}_{2}+\cdots+c_{n} \mathbf{x}_{n} \\] (b) Let \(X=\left(\mathbf{x}_{1}, \ldots, \mathbf{x}_{n}\right)\) and \(\mathbf{c}=\left(c_{1}, \ldots, c_{n}\right)^{T}\) Assuming that the vectors \(\mathbf{x}_{1}, \ldots, \mathbf{x}_{n}\) are linearly independent, show that \(\mathbf{c}=X^{-1} \mathbf{Y}_{0}\)
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 \(T\)
Let \(p(\lambda)=(-1)^{n}\left(\lambda^{n}-a_{n-1} \lambda^{n-1}-\cdots-a_{1} \lambda-a_{0}\right)\) be a polynomial of degree \(n \geq 1\), and let \\[ C=\left(\begin{array}{ccccc} a_{n-1} & a_{n-2} & \cdots & a_{1} & a_{0} \\ 1 & 0 & \cdots & 0 & 0 \\ 0 & 1 & \cdots & 0 & 0 \\ \vdots & & & \\ 0 & 0 & \cdots & 1 & 0 \end{array}\right) \\] (a) Show that if \(\lambda_{i}\) is a root of \(p(\lambda)=0,\) then \(\lambda_{i}\) is an eigenvalue of \(C\) with eigenvector \(\mathbf{x}=\) \(\left(\lambda_{i}^{n-1}, \lambda_{i}^{n-2}, \ldots, \lambda_{i}, 1\right)^{T}\) (b) Use part (a) to show that if \(p(\lambda)\) has \(n\) distinct roots, then \(p(\lambda)\) is the characteristic polynomial of \(C\). The matrix \(C\) is called the companion matrix of \(p(\lambda)\)
Let \(A\) be a Hermitian matrix and let \(B=i A\). Show that \(B\) is skew Hermitian.
For each of the following, factor the given matrix into a product \(L D L^{T}\), where \(L\) is lower triangular with 1 's on the diagonal and \(D\) is a diagonal matrix: (a) \(\left(\begin{array}{rr}4 & 2 \\ 2 & 10\end{array}\right)\) (b) \(\left(\begin{array}{rr}9 & -3 \\ -3 & 2\end{array}\right)\) \((\mathrm{c})\left(\begin{array}{rrr}16 & 8 & 4 \\ 8 & 6 & 0 \\ 4 & 0 & 7\end{array}\right)\) (d) \(\left(\begin{array}{rrr}9 & 3 & -6 \\ 3 & 4 & 1 \\ -6 & 1 & 9\end{array}\right)\)
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