Chapter 2: Problem 53
Express each set in the simplest interval form. $$ [3,6] \cup(4,9) $$
Short Answer
Expert verified
[3, 9)
Step by step solution
01
- Identify the Sets
The given sets are \( [3, 6] \) and \( (4, 9) \). The first is a closed interval from 3 to 6, and the second is an open interval from 4 to 9.
02
- Understand Set Union
The union of two sets includes all points that are in either set. Therefore, it combines all elements from \( [3, 6] \) and \( (4, 9) \).
03
- Find the Overlapping Interval
The intervals \( [3, 6] \) and \( (4, 9) \) overlap between 4 and 6. Specifically, from \( [4, 6] \) part of the closed interval \( [3, 6] \) and part of the open interval \( (4, 9) \).
04
- Determine the Combined Set
Combine the intervals into one continuous interval. Starting from 3 (inclusive), through the overlapping section from 4 to 6, and continuing until 9 (not inclusive).
05
- Express in Simplified Interval Form
The simplest interval form for the union of the given sets is \( [3, 9) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Set Union
In math, a union merges different sets into a single set containing all unique elements from the original sets.
This is represented by the symbol \( \cup \), meaning 'union.' For sets A and B, the union includes all elements in A, all in B, and those in both.
For example, with sets \( [3, 6] \) and \( (4, 9) \), the union is written as \( [3, 6] \cup (4, 9) \). The result contains:
This is represented by the symbol \( \cup \), meaning 'union.' For sets A and B, the union includes all elements in A, all in B, and those in both.
For example, with sets \( [3, 6] \) and \( (4, 9) \), the union is written as \( [3, 6] \cup (4, 9) \). The result contains:
- Elements 3 to 6 (inclusive) from \( [3, 6] \)
- Elements greater than 4 and less than 9 from \( (4, 9) \)
Closed Interval
A closed interval includes its endpoints, represented with square brackets. For instance, the interval \( [3, 6] \) is closed because it includes 3, 4, 5, and 6.
This means the values at the boundaries are part of the set. To visualize, imagine a line segment from 3 to 6. Both 3 and 6 are part of this segment.
Closed intervals are useful when you need to consider every point within a given range, including the borders.
Example: The interval \( [a, b] \) means:
This means the values at the boundaries are part of the set. To visualize, imagine a line segment from 3 to 6. Both 3 and 6 are part of this segment.
Closed intervals are useful when you need to consider every point within a given range, including the borders.
Example: The interval \( [a, b] \) means:
- It includes all values from \(\text{a}\) to \(\text{b}\)
- It contains both \(\text{a}\) and \(\text{b}\)
Open Interval
An open interval does not include its endpoints, represented with parenthesis. For instance, \( (4, 9) \) is open because it includes values greater than 4 and less than 9, but not 4 and 9 themselves.
This means you never reach the edges, only points close to them. Think of an open interval as a line segment from which both boundary points are removed.
Example: The interval \( (a, b) \) means:
This means you never reach the edges, only points close to them. Think of an open interval as a line segment from which both boundary points are removed.
Example: The interval \( (a, b) \) means:
- It contains all values strictly between \(\text{a}\) and \(\text{b}\)
- It excludes \(\text{a}\) and \(\text{b}\)
Overlapping Intervals
Overlapping intervals share at least one common point. When this happens, you need to find and merge the shared parts.
The two intervals \( [3, 6] \) and \( (4, 9) \) overlap between 4 and 6. That means every number in this range belongs to both intervals.
In our example:
The two intervals \( [3, 6] \) and \( (4, 9) \) overlap between 4 and 6. That means every number in this range belongs to both intervals.
In our example:
- The common part is \( [4, 6] \).
- When we take the union, this helps us to determine the full span: from 3 (inclusive) to 9 (exclusive).