Chapter 1: Problem 23
Prove that if \(A\) is row equivalent to \(B\), then \(B\) is row equivalent to \(A\)
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Chapter 1: Problem 23
Prove that if \(A\) is row equivalent to \(B\), then \(B\) is row equivalent to \(A\)
These are the key concepts you need to understand to accurately answer the question.
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Given $$A=\left(\begin{array}{ll} 3 & 1 \\ 5 & 2 \end{array}\right) \quad \text { and } \quad B=\left(\begin{array}{ll} 1 & 2 \\ 3 & 4 \end{array}\right)$$ compute \(A^{-1}\) and use it to (a) find a \(2 \times 2\) matrix \(X\) such that \(A X=B\) (b) find a \(2 \times 2\) matrix \(Y\) such that \(Y A=B\)
Let \(A\) be an idempotent matrix. (a) Show that \(I-A\) is also idempotent. (b) Show that \(I+A\) is nonsingular and \((I+A)^{-1}=I-\frac{1}{2} A\)
Is the transpose of an elementary matrix an elementary matrix of the same type? Is the product of two elementary matrices an elementary matrix?
Let \(A\) be a nonsingular \(n \times n\) matrix and let \(B\) be an \(n \times r\) matrix. Show that the reduced row echelon form of \((A | B)\) is \((I | C),\) where \(C=A^{-1} B\)
Let \(U\) be an \(m \times m\) matrix, let \(V\) be an \(n \times n\) matrix, and let \\[ \Sigma=\left(\begin{array}{l} \Sigma_{1} \\ O \end{array}\right) \\] where \(\Sigma_{1}\) is an \(n \times n\) diagonal matrix with diagonal entries \(\sigma_{1}, \sigma_{2}, \ldots, \sigma_{n}\) and \(O\) is the \((m-n) \times n\) zero matrix. (a) Show that if \(U=\left(U_{1}, U_{2}\right),\) where \(U_{1}\) has \(n\) columns, then \\[ U \Sigma=U_{1} \Sigma_{1} \\] (b) Show that if \(A=U \Sigma V^{T},\) then \(A\) can be ex pressed as an outer product expansion of the form \\[ A=\sigma_{1} \mathbf{u}_{1} \mathbf{v}_{1}^{T}+\sigma_{2} \mathbf{u}_{2} \mathbf{v}_{2}^{T}+\cdots+\sigma_{n} \mathbf{u}_{n} \mathbf{v}_{n}^{T} \\]
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