Chapter 1: Problem 6
Let \(A=\\{x: x \in R,|x|<1\\}\)
\(B=\\{x: x \in R,|x-1| \geq 1\\}\)
and \(A \cup B=R-D\), then the set \(D\) is
(A) \(\\{x: 1
Short Answer
Expert verified
The set \(D\) is \([1, 2)\), which matches option (B).
Step by step solution
01
Understand the Given Sets
First, understand the sets \(A\) and \(B\). Set \(A=\{x: x \in \mathbb{R},|x|<1\}\) includes all real numbers \(x\) such that \(-1<x<1\). Set \(B=\{x: x \in \mathbb{R},|x-1| \geq 1\}\) means \(|x-1|\) is greater than or equal to 1, which results in \(x \leq 0\) or \(x \geq 2\).
02
Union of Sets A and B
Next, find \(A \cup B\). Since \(A\) includes all \(x\) where \(-1<x<1\), and \(B\) includes \(x \leq 0\) or \(x \geq 2\), the union \(A \cup B\) results in all \(x\) such that \(-1<x<1\) or \(x \geq 2\). In interval notation, this is \((-1,1) \cup [2, \infty)\).
03
Find Missing Elements in R
To find set \(D\), note that \(A \cup B = \mathbb{R} - D\). Hence, \(D\) represents the elements not included in \((-1,1) \cup [2, \infty)\). This means \(D = [1, 2)\), as this interval is not covered by the union of \(A\) and \(B\).
04
Match with Options
Finally, match the set \(D = [1, 2)\) with the given options. The correct option is (B) \(\{x: 1 \leq x < 2\}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Real Numbers
Real numbers are a fundamental part of mathematics and include all the numbers that can be found on the number line. This set encompasses:
- Natural numbers: 1, 2, 3, ...
- Whole numbers: 0, 1, 2, 3, ...
- Integers: ..., -3, -2, -1, 0, 1, 2, 3, ...
- Rational numbers: fractions like 1/2, 3/4, including numbers that can be expressed as a ratio of two integers.
- Irrational numbers: numbers like \sqrt{2} and \pi that cannot be expressed as a simple fraction.
Interval Notation
Interval notation is a concise way to describe subsets of real numbers. It helps in expressing ranges of numbers without listing every individual element. Here’s how it works:
- Closed interval [a, b]: Includes all numbers between a and b, as well as a and b themselves. The square brackets denote this inclusion.
- Open interval (a, b): Includes all numbers between a and b, but not a and b themselves. Round parentheses indicate exclusion.
- Semi-open intervals [a, b) or (a, b]: One boundary is included and the other is not, as shown by a combination of square bracket and round parenthesis.
Union of Sets
The union of sets in set theory is an operation that combines elements from two or more sets into a single set. The basic idea is that if an element is present in any of the original sets, it will be in the union:
- For example, if set \( A = \{1, 2, 3\} \) and set \( B = \{3, 4, 5\} \), then the union \( A \cup B = \{1, 2, 3, 4, 5\} \).
- The symbol "\cup" is used to denote union.
- Union is a commutative operation, meaning \( A \cup B = B \cup A \).
- It is also associative, so \( (A \cup B) \cup C = A \cup (B \cup C) \).