Chapter 3: Problem 7
Show that the element 0 in a vector space is unique.
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Chapter 3: Problem 7
Show that the element 0 in a vector space is unique.
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Let \(\mathbb{R}^{+}\) denote the set of positive real numbers. Define the operation of scalar multiplication, denoted ?, by $$\alpha \circ x=x^{\alpha}$$ for each \(x \in \mathbb{R}^{+}\) and for any real number \(\alpha\). Define the operation of addition, denoted \(\oplus,\) by $$x \oplus y=x \cdot y \quad \text { for all } \quad x, y \in \mathbb{R}^{+}$$ Thus, for this system, the scalar product of -3 \(\operatorname{times} \frac{1}{2}\) is given by $$-3 \circ \frac{1}{2}=\left(\frac{1}{2}\right)^{-3}=8$$ and the sum of 2 and 5 is given by $$2 \oplus 5=2 \cdot 5=10$$ Is \(\mathbb{R}^{+}\) a vector space with these operations? Prove your answer.
Let \(\mathbf{x}_{1}, \mathbf{x}_{2},\) and \(\mathbf{x}_{3}\) be linearly independent vectors in \(\mathbb{R}^{n}\) and let $$\mathbf{y}_{1}=\mathbf{x}_{1}+\mathbf{x}_{2}, \quad \mathbf{y}_{2}=\mathbf{x}_{2}+\mathbf{x}_{3}, \quad \mathbf{y}_{3}=\mathbf{x}_{3}+\mathbf{x}_{1}$$ Are \(\mathbf{y}_{1}, \mathbf{y}_{2},\) and \(\mathbf{y}_{3}\) linearly independent? Prove your answer.
Let \(S\) denote the set of all infinite sequences of real numbers with scalar multiplication and addition defined by $$\begin{aligned} \alpha\left\\{a_{n}\right\\} &=\left\\{\alpha a_{n}\right\\} \\ \left\\{a_{n}\right\\}+\left\\{b_{n}\right\\} &=\left\\{a_{n}+b_{n}\right\\} \end{aligned}$$ Show that \(S\) is a vector space.
Show that if a matrix \(U\) is in row echelon form, then the nonzero row vectors of \(U\) form a basis for the row space of \(U\).
Consider the vectors \\[ \mathbf{x}_{1}=\left(\begin{array}{l} 2 \\ 1 \end{array}\right), \quad \mathbf{x}_{2}=\left[\begin{array}{l} 4 \\ 3 \end{array}\right], \quad \mathbf{x}_{3}=\left[\begin{array}{r} 7 \\ -3 \end{array}\right] \\] (a) Show that \(x_{1}\) and \(x_{2}\) form a basis for \(\mathbb{R}^{2}\) (b) Why must \(\mathbf{x}_{1}, \mathbf{x}_{2},\) and \(\mathbf{x}_{3}\) be linearly dependent? (c) What is the dimension of \(\operatorname{Span}\left(\mathbf{x}_{1}, \mathbf{x}_{2}, \mathbf{x}_{3}\right) ?\)
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