Chapter 1: Problem 16
Write the union of the two intervals as a single interval. $$ (-\infty, 0] \text { and }[0,3) $$
Short Answer
Expert verified
The union of the intervals is
\((-\infty, 3)\).
Step by step solution
01
Identify the Type of Intervals
The first interval is \((-\infty, 0]\), which is open on the left and closed on the right. The second interval is \([0, 3)\), which is closed on the left and open on the right.
02
Analyze the Overlapping Point
Both intervals include the point 0. The first interval ends with 0 included, \(0]\), and the second interval starts with 0 included, \([0\). Thus, the point 0 is covered by both intervals.
03
Determine the Complete Coverage
The first interval extends from \(-\infty\) to 0, and the second interval starts from 0 and goes to 3. Together, these intervals cover from \(-\infty\) to 3 without any gaps.
04
Write the Single Union Interval
Since the intervals overlap or connect at point 0, combine them as \((-\infty, 3)\). The full range is open at \(-\infty\) and terminates just before 3.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Interval Union
When dealing with interval notation in mathematics, an **interval union** is used to combine overlapping or connected intervals into a single, comprehensive interval. This is especially relevant when intervals have a common point or overlap completely or partially. To unite these intervals:
- Identify their common boundary points.
- Consider the openness or closedness of each endpoint.
- Combine them into a unified interval that reflects the full span covered by all individual intervals together.
Open and Closed Intervals
Understanding the difference between **open and closed intervals** is fundamental in interval notation. An interval is essentially a portion of numbers along the real number line enclosed between two endpoints.
- **Open Intervals**: These do not include their endpoint(s). For instance, in the interval \((a, b)\), neither \(a\) nor \(b\) is included. The notation uses round brackets.
- **Closed Intervals**: These include their endpoint(s). For example, in the interval \([a, b]\), both \(a\) and \(b\) are part of the set. Square brackets denote this inclusion.
- **Half-Open/Half-Closed Intervals**: These contain one endpoint but not the other, like \([a, b)\) or \((a, b]\).
Real Number Line
The **real number line** is a straight, infinitely extending line that visually represents all possible real numbers. Each point on this line corresponds to a real number, and it is used to illustrate various mathematical concepts like intervals, functions, and inequalities. Key aspects include:
- **Infinite Extent**: It stretches infinitely in both the positive and negative directions, often noted as \(\infty\) and \(-\infty\).
- **Visual Representation**: On a graph, intervals on the real number line are depicted by shaded regions with endpoints marked by open or closed circles, indicating whether these points are included in the interval.
- **Utility in Understanding**: Applying intervals to the real number line helps in visually comprehending concepts like union, intersection, and completeness of the number set.