Chapter 1: Problem 26
Prove that \(B\) is row equivalent to \(A\) if and only if there exists a nonsingular matrix \(M\) such that \(B=M A\)
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Chapter 1: Problem 26
Prove that \(B\) is row equivalent to \(A\) if and only if there exists a nonsingular matrix \(M\) such that \(B=M A\)
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For each of the following pairs of matrices, find an elementary matrix \(E\) such that \(A E=B:\) (a) \(A=\left(\begin{array}{lll}4 & 1 & 3 \\ 2 & 1 & 4 \\ 1 & 3 & 2\end{array}\right), B=\left(\begin{array}{lll}3 & 1 & 4 \\ 4 & 1 & 2 \\ 2 & 3 & 1\end{array}\right)\) (b) \(A=\left(\begin{array}{ll}2 & 4 \\ 1 & 6\end{array}\right), B=\left(\begin{array}{rr}2 & -2 \\ 1 & 3\end{array}\right)\) (c) \(A=\left(\begin{array}{rrr}4 & -2 & 3 \\ -2 & 4 & 2 \\ 6 & 1 & -2\end{array}\right)\) \(B=\left(\begin{array}{rrr}2 & -2 & 3 \\ -1 & 4 & 2 \\ 3 & 1 & -2\end{array}\right)\)
Let \(A\) be a \(2 \times 2\) matrix with \(a_{11} \neq 0\) and let \(\alpha=a_{21} / a_{11} .\) Show that \(A\) can be factored into a product of the form $$\left(\begin{array}{ll} 1 & 0 \\ \alpha & 1 \end{array}\right)\left(\begin{array}{cc} a_{11} & a_{12} \\ 0 & b \end{array}\right)$$ What is the value of \(b ?\)
Let \\[ A=\left(\begin{array}{cc} A_{11} & A_{12} \\ O & A_{22} \end{array}\right) \\] where all four blocks are \(n \times n\) matrices. (a) If \(A_{11}\) and \(A_{22}\) are nonsingular, show that \(A\) must also be nonsingular and that \(A^{-1}\) must be of the form \\[ \left(\begin{array}{c|c} A_{11}^{-1} & C \\ \hline O & A_{22}^{-1} \end{array}\right) \\] (b) Determine \(C\)
Given \\[ X=\left(\begin{array}{lll} 2 & 1 & 5 \\ 4 & 2 & 3 \end{array}\right) \quad Y=\left[\begin{array}{lll} 1 & 2 & 4 \\ 2 & 3 & 1 \end{array}\right] \\] (a) Compute the outer product expansion of \(X Y^{T}\) (b) Compute the outer product expansion of \(Y X^{T}\) How is the outer product expansion of \(Y X^{T}\) related to the outer product expansion of \(X Y^{T} ?\)
Let \\[ A=\left(\begin{array}{ll} O & I \\ B & O \end{array}\right) \\] where all four submatrices are \(k \times k\). Determine \(A^{2}\) and \(A^{4}\)
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