Chapter 7: Problem 1
Find the three-digit decimal floating-point representation of each of the following numbers: (a) 2312 (b) 32.56 (c) 0.01277 (d) 82,431
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Chapter 7: Problem 1
Find the three-digit decimal floating-point representation of each of the following numbers: (a) 2312 (b) 32.56 (c) 0.01277 (d) 82,431
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Let \\[ A=\left(\begin{array}{ll} 3 & 2 \\ 1 & 1 \end{array}\right) \quad \text { and } \quad \mathbf{b}=\left(\begin{array}{l} 5 \\ 2 \end{array}\right) \\] The solution computed using two-digit decimal floating-point arithmetic is \(\mathbf{x}=(1.1,0.88)^{T}\) (a) Determine the residual vector \(\mathbf{r}\) and the value of the relative residual \(\|\mathbf{r}\|_{\infty} /\|\mathbf{b}\|_{\infty}\) (b) Find the value of \(\operatorname{cond}_{\infty}(A)\) (c) Without computing the exact solution, use the results from parts (a) and (b) to obtain bounds for the relative error in the computed solution. (d) Compute the exact solution \(\mathbf{x}\) and determine the actual relative error. Compare your results with the bounds derived in part (c)
If \(D\) is an \(n \times n\) diagonal matrix, how do the values of \(\|D\|_{1},\|D\|_{2},\) and \(\|D\|_{\infty}\) compare? Explain your answers.
Show that if \(D\) is an \(n \times n\) diagonal matrix, then \\[ \|D\|_{2}=\max _{1 \leq i \leq n}\left(\left|d_{i i}\right|\right) \\]
Let \(\mathbf{u}\) be a unit vector in \(\mathbb{R}^{n}\) and let \\[ Q=I-2 \mathbf{u u}^{T} \\] (a) Show that \(\mathbf{u}\) is an eigenvector of \(Q .\) What is the corresponding eigenvalue? (b) Let \(\mathbf{z}\) be a nonzero vector in \(\mathbb{R}^{n}\) that is orthogonal to u. Show that \(z\) is an eigenvector of \(Q\) belonging to the eigenvalue \(\lambda=1\) (c) Show that the eigenvalue \(\lambda=1\) must have multiplicity \(n-1 .\) What is the value of \(\operatorname{det}(Q) ?\)
Let \\[ A=\left(\begin{array}{ll} 1 & 1 \\ 1 & 1 \\ 0 & 0 \end{array}\right) \\] Determine \(A^{+}\) and verify that \(A\) and \(A^{+}\) satisfy the four Penrose conditions (see Example 1 of Section 5 ).
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