Chapter 11: Problem 16
Solve each inequality. Write the solution set in interval notation. See Example 4. $$ \frac{x-5}{x-6}>0 $$
Short Answer
Expert verified
\((-\infty, 5) \cup (6, \infty)\)
Step by step solution
01
Find Critical Points
Start by identifying the values of \( x \) that make the expression \( \frac{x-5}{x-6} = 0 \) or undefined. The expression equals zero when the numerator is zero. So, set \( x-5=0 \) and solve for \( x \): \( x=5 \). The expression is undefined when the denominator is zero. So, set \( x-6=0 \) and solve for \( x \): \( x=6 \). Thus, the critical points are \( x=5 \) and \( x=6 \).
02
Number Line and Intervals
Plot the critical points, 5 and 6, on a number line. These points divide the number line into three intervals: \((-\infty, 5)\), \((5, 6)\), and \((6, \infty)\).
03
Test Intervals
Choose a test point from each interval to determine if the inequality is satisfied.- For \((-\infty, 5)\), use \(x=0\): \( \frac{0-5}{0-6} = \frac{-5}{-6} > 0\).- For \((5, 6)\), use \(x=5.5\): \( \frac{5.5-5}{5.5-6} = \frac{0.5}{-0.5} < 0\).- For \((6, \infty)\), use \(x=7\): \( \frac{7-5}{7-6} = \frac{2}{1} > 0\).
04
Combine Results
The inequality \( \frac{x-5}{x-6}>0 \) is satisfied in the intervals where the result is positive. Based on our tests, these intervals are \((-\infty, 5)\) and \((6, \infty)\).
05
Write Solution in Interval Notation
The solution set in interval notation includes both intervals where the expression is positive. So, the solution is \((-\infty, 5) \cup (6, \infty)\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Critical Points
When solving inequalities like \( \frac{x-5}{x-6}>0 \), the first step is to find the critical points. These are values of \( x \) that make the expression either zero or undefined. This gives us crucial information about where the expression might change sign.
Let's break this down:
Let's break this down:
- Zero: The expression equals zero when its numerator is zero. Here, setting \( x-5=0 \) gives \( x=5 \).
- Undefined: The expression is undefined when its denominator is zero. Setting \( x-6=0 \) results in \( x=6 \).
Interval Notation
Once we have the critical points, we can use them to write intervals. With \( x=5 \) and \( x=6 \), the number line is divided into three intervals:
This notation is a compact and efficient way to communicate the solution space on a number line.
- \(( -\infty, 5)\)
- \((5, 6)\)
- \((6, \infty)\)
This notation is a compact and efficient way to communicate the solution space on a number line.
Test Intervals
With the intervals established, we choose a test point from each to determine where the inequality is true. Testing in each interval helps us decide if the expression \( \frac{x-5}{x-6} > 0 \) holds.
- \(( -\infty, 5)\): Choose \( x = 0 \). Substituting gives \( \frac{0-5}{0-6}= \frac{-5}{-6} > 0 \), confirming that this interval satisfies the inequality.
- \((5, 6)\): Choose \( x = 5.5 \). Here, \( \frac{5.5-5}{5.5-6}= \frac{0.5}{-0.5} < 0 \), so this interval does not satisfy the inequality.
- \((6, \infty)\): Choose \( x = 7 \). Calculations give \( \frac{7-5}{7-6}=\frac{2}{1} > 0 \), so this interval satisfies the inequality.