Big Ideas Math Integrated I, 2016
BI
Big Ideas Math Integrated I, 2016 View details
6. Solving Absolute Value Inequalities
Continue to next subchapter

Exercise 38 Page 92

Remember that an absolute value represents a distance from a midpoint.

First graph: |x-2|≥3
Second graph: |x-2|<3
Third graph: |x-2|≤3
Fourth graph: |x-2|>3
Explanation: See solution.

Practice makes perfect

Before we can write the inequalities for the given graphs, we should remember two key things.

  1. An absolute value equation is written as |x-a|=b, where a is the midpoint on the number line and b is distance from the midpoint to either endpoint.
  2. The midpoint can be found as the mean of the two endpoints P_1 and P_2.

Midpoint=P_1+P_2/2 Let's work on each graph separately.

First Graph

Consider the given graph.

We can see that the endpoints are -1 and 5. Knowing this we can find the midpoint.
Midpoint=P_1+P_2/2
Midpoint=-1+ 5/2
Midpoint=4/2
Midpoint=2
The midpoint at 2 is at a distance of 3 from -1 and 5. Therefore, we can write the absolute value equation. |x- 2|= 3 In order to write it as an absolute value inequality, we first notice in the graph that the endpoints are closed. This means that the inequality is non-strict. Since the solution set includes points that are farther away from the endpoints, the distance is greater than or equal to 3. |x-2|≥3

Second Graph

Consider the given graph.

Since this graph has the same endpoints, the midpoint is also 2. We can write the same absolute value equation. |x-2|=3 In order to write it as an absolute value inequality, we first notice in the graph that the endpoints are open. This means that the inequality is strict. Since the solution set includes points that are between the endpoints, the distance is less than 3. |x-2|<3

Third Graph

Consider the given graph.

Since this graph has the same endpoints, the midpoint is also 2. We can write the same absolute value equation. |x-2|=3 In order to write it as an absolute value inequality, we first notice in the graph that the endpoints are closed. This means that the inequality is non-strict. Since the solution set includes points that are between the endpoints, the distance is less than or equal to 3. |x-2|≤ 3

Fourth Graph

Consider the given graph.

Since this graph has the same endpoints, the midpoint is also 2. We can write the same absolute value equation. |x-2|=3 In order to write it as an absolute value inequality, we first notice in the graph that the endpoints are open. This means that the inequality is strict. Since the solution set includes points that are farther away from the endpoints, the distance is greater than 3. |x-2|>3