Chapter 1: Problem 49
The set of real numbers satisfying the given inequality is one or more intervals on the number line. Show the interval(s) on a number line. $$|x|<4$$
Short Answer
Expert verified
The solution interval is \((-4, 4)\) on the number line.
Step by step solution
01
Interpret the Absolute Value Inequality
The inequality \(|x| < 4\) means that the distance of \(x\) from 0 on the number line is less than 4.
02
Remove the Absolute Value
The expression \(|x| < 4\) can be rewritten as two separate inequalities: \(x > -4\) and \(x < 4\). This is because \(|x|\) represents how far away \(x\) is from 0 regardless of direction.
03
Identify the Solution Interval
Combine the inequalities from Step 2 to form the compound inequality \(-4 < x < 4\). This represents the set of all \(x\) values that satisfy both \(x > -4\) and \(x < 4\).
04
Express the Solution Interval Using Interval Notation
The solution to the inequality is expressed in interval notation as \((-4, 4)\). This interval includes all real numbers between -4 and 4, but not inclusive of -4 and 4 themselves.
05
Visualize on a Number Line
On a number line, sketch the interval \((-4, 4)\). Typically, open circles are drawn at -4 and 4 to indicate that these endpoints are not included in the interval. A line is drawn between these circles to show all numbers between them are included.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Number Line Representation
Representing inequalities on a number line can make understanding them much simpler. A number line visually shows where the set of all solutions falls along the real number continuum. For the inequality \(|x| < 4\), you want to represent all the values of \(x\) that have an absolute distance from 0 that is less than 4. To do this:
- Place open circles on -4 and 4 to represent that these values are not included in the solution (since the inequality uses \(<\), not \(\leq\)).
- Draw a line connecting these open circles to show that every value between -4 and 4 is part of the solution set.
- This line visually confirms that any number you pick inside this highlighted segment will satisfy \(|x| < 4\).
Interval Notation
Interval notation is a shorthand way to write the solution set of an inequality, capturing the beginning and end of an interval. For \(|x| < 4\), the interval notation is \((-4, 4)\). This notation presents:
- A parenthesis \(()\) on both sides, indicating that -4 and 4 are not included in the solutions since it’s an open interval due to the \(<\) operator.
- The values inside the parentheses, -4 and 4, are the boundaries of the solution set.
- Brackets \([\cdot, \cdot]\) would be used if 4 and -4 were included, which would occur with \(\leq\) or \(\geq\) inequalities.
- Always consider the context in question to determine if you need open or closed intervals.
Compound Inequalities
Compound inequalities involve combining two separate inequalities into one. The expression \(|x| < 4\) creates two conditions for the variable \(x\):
- \(x > -4\)
- \(x < 4\)
- "And" logic, meaning \(x\) must meet both conditions at the same time.
- Provides a clear picture of the set of all \(x\) values that satisfy the inequality.