Chapter 2: Problem 30
$$ \text { Prove that the subspaces }\\{0\\}, V, R(T) \text {, and } N(T) \text { are all } T \text {-invariant. } $$
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Chapter 2: Problem 30
$$ \text { Prove that the subspaces }\\{0\\}, V, R(T) \text {, and } N(T) \text { are all } T \text {-invariant. } $$
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Let \(\beta\) be an ordered basis for a finite-dimensional vector space \(\mathrm{V}\), and let \(\mathrm{T}: \mathrm{V} \rightarrow \mathrm{V}\) be linear. Prove that, for any nonnegative integer \(k\), \(\left[\mathrm{T}^{k}\right]_{\beta}=\left([\mathrm{T}]_{\beta}\right)^{k} .\)
Let \(\mathrm{T}: \mathrm{P}(R) \rightarrow \mathrm{P}(R)\) be defined by \(\mathrm{T}(f(x))=f^{\prime}(x)\). Recall that \(\mathrm{T}\) is linear. Prove that \(\mathrm{T}\) is onto, but not one-to-one.
Using the notation in the definition above, assume that \(T: V \rightarrow V\) is the projection on \(\mathrm{W}_{1}\) along \(\mathrm{W}_{2}\). (a) Prove that \(\mathrm{T}\) is linear and \(\mathrm{W}_{1}=\\{x \in \mathrm{V}: \mathrm{T}(x)=x\\}\). (b) Prove that \(\mathrm{W}_{1}=\mathrm{R}(\mathrm{T})\) and \(\mathrm{W}_{2}=\mathrm{N}(\mathrm{T})\). (c) Describe \(\mathrm{T}\) if \(\mathrm{W}_{1}=\mathrm{V}\). (d) Describe \(T\) if \(W_{1}\) is the zero subspace.
Let \(\mathrm{V}\) be an \(n\)-dimensional vector space, and let \(\mathrm{T}: \mathrm{V} \rightarrow \mathrm{V}\) be a linear transformation. Suppose that \(\mathrm{W}\) is a T-invariant subspace of \(\mathrm{V}\) (see the exercises of Section 2.1) having dimension \(k\). Show that there is a basis \(\beta\) for \(\mathrm{V}\) such that \([\mathrm{T}]_{\beta}\) has the form $$ \left(\begin{array}{ll} A & B \\ O & C \end{array}\right), $$ where \(A\) is a \(k \times k\) matrix and \(O\) is the \((n-k) \times k\) zero matrix.
Let \(A\) and \(B\) be matrices for which the product matrix \(A B\) is defined, and let \(u_{j}\) and \(v_{j}\) denote the \(j\) th columns of \(A B\) and \(B\), respectively. If \(v_{p}=c_{1} v_{j_{1}}+c_{2} v_{j_{2}}+\cdots+c_{k} v_{j_{k}}\) for some scalars \(c_{1}, c_{2}, \ldots c_{k}\), prove that \(u_{p}=c_{1} u_{j_{1}}+c_{2} u_{j_{2}}+\cdots+c_{k} u_{j_{k}} .\) Visit goo.gl/sRpves for a solution.
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