Chapter 1: Problem 38
Solve the inequalities in Exercises \(35-42 .\) Express the solution sets as intervals or unions of intervals and show them on the real line. Use the result \(\sqrt{a^{2}}=|a|\) as appropriate. $$ \frac{1}{9} < x^{2} < \frac{1}{4} $$
Short Answer
Expert verified
The solution is \( \left( \frac{1}{3}, \frac{1}{2} \right) \cup \left( -\frac{1}{2}, -\frac{1}{3} \right) \).
Step by step solution
01
Understand the Inequality
We are given a compound inequality \( \frac{1}{9} < x^2 < \frac{1}{4} \). This means that the square of \( x \) is between \( \frac{1}{9} \) and \( \frac{1}{4} \). Our task is to find the values of \( x \) that make this inequality true.
02
Solve the Left Inequality
Let's first solve the inequality \( x^2 > \frac{1}{9} \). Rewrite this inequality as \( x^2 - \frac{1}{9} > 0 \). Thus, \( x^2 > \frac{1}{9} \) implies \( x > \frac{1}{3} \) or \( x < -\frac{1}{3} \).
03
Solve the Right Inequality
Now solve \( x^2 < \frac{1}{4} \). Rewrite this as \( x^2 - \frac{1}{4} < 0 \). Thus, \( x^2 < \frac{1}{4} \) implies \( -\frac{1}{2} < x < \frac{1}{2} \).
04
Combine the Solutions
The solution to the original compound inequality \( \frac{1}{9} < x^2 < \frac{1}{4} \) is the intersection of the solution sets from the left and right inequalities. Therefore, the solution in terms of \( x \) will be the values that satisfy both: \( \frac{1}{3} < x < \frac{1}{2} \) or \(-\frac{1}{2} < x < -\frac{1}{3} \).
05
Express as Intervals
Express the solution as two intervals: \( \left( \frac{1}{3}, \frac{1}{2} \right) \cup \left( -\frac{1}{2}, -\frac{1}{3} \right) \).
06
Show on the Number Line
On a number line, mark the intervals \( \left( \frac{1}{3}, \frac{1}{2} \right) \) and \( \left( -\frac{1}{2}, -\frac{1}{3} \right) \) as open intervals where \( x \) is valid. These are shown as two separate segments without endpoints.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Compound Inequality
A compound inequality involves two inequalities that are combined in one statement. Here, we have \( \frac{1}{9} < x^2 < \frac{1}{4} \).This means that the square of \( x \) must be greater than \( \frac{1}{9} \) as well as less than \( \frac{1}{4} \). Essentially, you are looking for the values of \( x \) that satisfy both conditions part of the same expression.
To solve a compound inequality, you can break it down into two separate inequalities, solve them individually, and then find the intersection of their solution sets.
To solve a compound inequality, you can break it down into two separate inequalities, solve them individually, and then find the intersection of their solution sets.
- The first part is \( x^2 > \frac{1}{9} \), which simplifies to \( x > \frac{1}{3} \) or \( x < -\frac{1}{3} \).
- The second part is \( x^2 < \frac{1}{4} \), giving us \( -\frac{1}{2} < x < \frac{1}{2} \).
Interval Notation
Interval notation is a convenient way of writing the solution to an inequality as a range of numbers. It involves using parentheses \(()\) and brackets \([]\) to express open and closed intervals.
For our compound inequality, the solution set is expressed as two open intervals:
For our compound inequality, the solution set is expressed as two open intervals:
- \((\frac{1}{3}, \frac{1}{2})\) indicates numbers greater than \(\frac{1}{3}\) and less than \(\frac{1}{2}\).
- \((-\frac{1}{2}, -\frac{1}{3})\) indicates numbers less than \(-\frac{1}{3}\) and greater than \(-\frac{1}{2}\).
Number Line Representation
Number line representation is a visual way to show solutions to inequalities. This can help you quickly and easily see the range of solutions.
On a number line:
On a number line:
- The part \((\frac{1}{3}, \frac{1}{2})\) is represented as a segment between \(\frac{1}{3}\) and \(\frac{1}{2}\), with open circles on \(\frac{1}{3}\) and \(\frac{1}{2}\) to show that these endpoints are not included.
- Similarly, \((-\frac{1}{2}, -\frac{1}{3})\) is shown with a segment between \(-\frac{1}{2}\) and \(-\frac{1}{3}\), also with open circles.
Square Root Property
The square root property is a crucial concept when dealing with inequalities involving square terms, such as \( x^2 \).
This property indicates that \( \sqrt{a^2} = |a| \). Thus, when we are solving inequalities like \( x^2 > \frac{1}{9} \) or \( x^2 < \frac{1}{4} \), we need to consider both positive and negative roots.
This property indicates that \( \sqrt{a^2} = |a| \). Thus, when we are solving inequalities like \( x^2 > \frac{1}{9} \) or \( x^2 < \frac{1}{4} \), we need to consider both positive and negative roots.
- For \( x^2 > \frac{1}{9} \), the solutions translate to \( x > \frac{1}{3} \) and \( x < -\frac{1}{3} \), indicating two potential ranges.
- For \( x^2 < \frac{1}{4} \), the result yields \( -\frac{1}{2} < x < \frac{1}{2} \) due to the square root covering both potential sign scenarios.