Chapter 2: Problem 8
Find all \(x \in \mathbb{R}\) that satisfy the following inequalities. (a) \(|x-1|>|x+1|\), (b) \(|x|+|x+1|<2\).
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Chapter 2: Problem 8
Find all \(x \in \mathbb{R}\) that satisfy the following inequalities. (a) \(|x-1|>|x+1|\), (b) \(|x|+|x+1|<2\).
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Show that if \(A\) and \(B\) are bounded subsets of \(\mathbb{R}\), then \(A \cup B\) is a bounded set. Show that \(\sup (A \cup B)=\sup \\{\sup A, \sup B\\}\)
Given any \(x \in \mathbb{R}\), show that there exists a unique \(n \in
\mathbb{Z}\) such that \(n-1 \leq x
Use Mathematical Induction to show that if \(a \in \mathbb{R}\) and \(m, n, \in \mathbb{N}\), then \(a^{m+n}=a^{m} a^{n}\) and \(\left(a^{m}\right)^{n}=a^{m n} .\)
Let \(X\) and \(Y\) be nonempty sets and let \(h: X \times Y \rightarrow \mathbb{R}\) have bounded range in \(\mathbb{R}\). Let \(f: X \rightarrow \mathbb{R}\) and \(g: Y \rightarrow \mathbb{R}\) be defined by $$ f(x):=\sup (h(x, y): y \in Y\\}, \quad g(y):=\inf \\{h(x, y): x \in X\\} $$ Prove that $$ \sup \\{g(y): y \in Y\\} \leq \inf \\{f(x): x \in X\\} $$ We sometimes express this by writing $$ \sup _{y} \inf _{x} h(x, y) \leq \inf _{x} \sup _{y} h(x, y) $$ Note that Exercises 8 and 9 show that the inequality may be either an equality or a strict inequality.
Let \(S\) be a bounded set in \(\mathbb{R}\) and let \(S_{0}\) be a nonempty subset of \(S .\) Show that inf \(S \leq\) inf \(S_{0} \leq\) \(\sup S_{0} \leq \sup S\)
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