Chapter 4: Problem 26
Extend \(\left\\{u_{1}=(1,1,1,1), u_{2}=(2,2,3,4)\right\\}\) to a basis of \(\mathbf{R}^{4}\).
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Chapter 4: Problem 26
Extend \(\left\\{u_{1}=(1,1,1,1), u_{2}=(2,2,3,4)\right\\}\) to a basis of \(\mathbf{R}^{4}\).
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Let \(U_{1}, U_{2}, U_{3}\) be the following subspaces of \(\mathbf{R}^{3}\) : \\[U_{1}=\\{(a, b, c): a=c\\}, \quad U_{2}=\\{(a, b, c): a+b+c=0\\}, \quad U_{3}=\\{(0,0, c)\\}\\] Show that \((\mathrm{a}) \mathbf{R}^{3}=U_{1}+U_{2},\) (b) \(\mathbf{R}^{3}=U_{2}+U_{3},(\mathrm{c}) \mathbf{R}^{3}=U_{1}+U_{3} .\) When is the sum direct?
Find a basis and the dimension of the subspace \(W\) of \(\mathbf{P}(t)\) spanned by (a) \(u=t^{3}+2 t^{2}-2 t+1, \quad v=t^{3}+3 t^{2}-3 t+4, \quad w=2 t^{3}+t^{2}-7 t-7\), (b) \(u=t^{3}+t^{2}-3 t+2, \quad v=2 t^{3}+t^{2}+t-4, \quad w=4 t^{3}+3 t^{2}-5 t+2\).
Let the rows of \(A \in M_{n \times n}(F)\) be \(a_{1}, a_{2}, \ldots, a_{n}\), and let \(B\) be the matrix in which the rows are $a_{n}, a_{n-1}, \ldots, a_{1}\(. Calculate \)\operatorname{det}(B)\( in terms of \)\operatorname{det}(A)$.
In Exercises 5- 12, evaluate the determinant of the given matrix by cofactor expansion along the indicated row. $$ \left(\begin{array}{rrr} 0 & 1 & 2 \\ -1 & 0 & -3 \\ 2 & 3 & 0 \end{array}\right) $$ along the first row
Let \(V\) be the set of ordered pairs \((a, b)\) of real numbers with addition in \(V\) and scalar multiplication on \(V\) defined by \\[(a, b)+(c, d)=(a+c, \quad b+d) \quad \text { and } \quad k(a, b)=(k a, 0)\\] Show that \(V\) satisfies all the axioms of a vector space except \(\left[\mathrm{M}_{4}\right]\) -that is, except \(1 u=u\). Hence, \(\left[\mathrm{M}_{4}\right]\) is not a consequence of the other axioms.
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