How to Graph Absolute Value Inequalities?

How to Graph Absolute Value Inequalities?

Graphing absolute value inequalities on the coordinate plane combines two skills: graphing the related absolute value equation (the boundary V) and determining which region to shade. The result is a shaded half-plane on one or both sides of the V-shaped boundary. This guide walks through the process step by step, with worked examples, two video lessons, and practice problems.

Tutor-style math help

Graph Absolute Value Inequalities: what to notice and how to work it

Inequalities skill
Inequalities describe a set of possible values. Solve the boundary like an equation, then decide which side of the boundary makes the statement true.

What to notice first

Watch the comparison sign from the first line to the last. Multiplying or dividing by a negative reverses the direction.

Common student mistake

Do not forget open and closed endpoints. Strict signs use open circles; signs with equals use closed circles.

Key formulas and cues

\(a<b\)
\(a\le b\)
\(\text{multiply/divide by a negative} \Rightarrow \text{reverse the sign}\)
\(|x-a|<b \Rightarrow a-b<x<a+b\)
vertex

A reliable path

  1. Solve the boundaryTemporarily treat the inequality like an equation.
  2. Choose the sideUse the sign or test a number if the direction is not obvious.
  3. Graph the solutionUse the correct endpoint and shade the values that work.

Worked examples

Flip the sign

Example: \(-3x>12\)
  1. Divide both sides by -3.
  2. Reverse the inequality sign.
  3. Simplify 12 divided by -3.
Answer: \(x<-4\)

Keep the sign

Example: \(x+5\le9\)
  1. Subtract 5 from both sides.
  2. No negative multiplication or division happened.
  3. Keep the sign direction.
Answer: \(x\le4\)
Try one before moving on
Try: Solve \(-2x\le10\).
Answer: \(x\ge-5\). Divide by -2 and flip the sign.
Next step: do the matching worksheet or quiz while the method is still fresh, then come back and explain the first step in your own words.

What Is an Absolute Value Inequality on a Graph?

An absolute value inequality in two variables, such as \(\color{blue}{y < |x|}\) or \(\color{blue}{y \ge |x - 2| + 1}\), defines a region of the coordinate plane. The boundary is the V-shaped graph of the related equation. Whether that boundary is solid or dashed depends on whether the inequality includes “equal to” (≤ or ≥) or not (< or >).

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How to Graph an Absolute Value Inequality

Step 1: Graph the Boundary

Replace the inequality symbol with an equals sign and graph the absolute value equation. This gives you the V-shaped boundary.

  • Use a solid line (or solid V) for ≤ or ≥.
  • Use a dashed line (or dashed V) for < or >.

Step 2: Identify the Vertex and Arms

Write the equation in the form \(\color{blue}{y = a}\)|\(\color{blue}{x – h}\)| + k. The vertex is (h, k). Determine whether the V opens up (a > 0) or down (a < 0).

Step 3: Test a Point

Choose a test point NOT on the boundary (the origin (0, 0) works unless it is on the boundary). Substitute it into the inequality:

  • If the inequality is true, shade the region containing the test point.
  • If the inequality is false, shade the opposite region.

Shading Shortcut

  • y < |expression| or y ≤ |expression|: shade below (and outside) the V.
  • y > |expression| or y ≥ |expression|: shade above (inside) the V.

Step-by-Step Summary

  1. Write the related equation by replacing the inequality symbol \(\color{blue}{\text{ with } =}\).
  2. Find the vertex (h, k) and the direction the V opens.
  3. Draw the boundary: solid for ≤ or ≥; dashed for < or >.
  4. Test a point not on the boundary in the original inequality.
  5. Shade the region where the inequality is true.

Watch: Graphing Absolute Value Inequalities (Video Lesson)

Khan Academy demonstrates how to graph absolute value inequalities on the coordinate plane:


Graphing Absolute Value Inequalities – Worked Examples

Example 1: Graph \(\color{blue}{y < |x|}\)

Boundary: y = |x|; vertex (0, 0); dashed V (strict <).
Test (0, −1): −1 < |0| = 0 → −1 < 0 ✓ (true)
Shade below the dashed V.

Example 2: Graph \(\color{blue}{y \ge |x – 2| + 1}\)

Boundary: y = |\(\color{blue}{x – 2}\)| + 1; vertex (2, 1); solid V (includes equal to).
Test (2, 5): 5 ≥ |\(\color{blue}{2-2}\)|+\(\color{blue}{1 = 1}\) ✓ (true)
Shade above and on the solid V (inside the V arms).

Example 3: Graph \(\color{blue}{y \le -|x + 1| + 4}\)

Boundary: y = −|\(\color{blue}{x + 1}\)| + 4; vertex (−1, 4); opens down; solid V.
Test (0, 0): 0 ≤ −|\(\color{blue}{0+1}\)|+4 = −\(\color{blue}{1+4 = 3}\) ✓ (true)
Shade below and on the solid downward V.

Example 4: Graph \(\color{blue}{y > 2|x – 3| – 2}\)

Boundary: \(\color{blue}{y = 2}\)|\(\color{blue}{x-3}\)|−2; vertex (3, −2); dashed V, steeper arms.
Test (3, 0): 0 > 2|\(\color{blue}{3-3}\)|−2 = −2 ✓ (true)
Shade above the dashed V (the interior region).

More Practice: Solving and Graphing Absolute Value Inequalities (Video Lesson)

Math and Science provides an in-depth walkthrough of both solving and graphing absolute value inequalities:


Exercises: Graphing Absolute Value Inequalities

  1. Graph \(\color{blue}{y > |x + 3|}\). State the vertex and the shaded region.
  2. Graph \(\color{blue}{y \le |x| – 2}\). Is the boundary solid or dashed?
  3. What is the vertex of the boundary for \(\color{blue}{y < -|x - 1| + 5}\)?
  4. Describe the shaded region for \(\color{blue}{y \ge 3|x|}\).
  5. For \(\color{blue}{y < |2x - 4| + 1}\), test the point (2, 0). Is it in the solution region?
  6. Write an absolute value inequality whose graph has vertex (0, 3), opens up, with shading above the boundary.

Answers

  1. Vertex (−3, 0); dashed V; shade above (inside) the V.
  2. Solid boundary; shade below (outside) the V; vertex (0, −2).
  3. Vertex (1, 5).
  4. Above and on the V; vertex (0, 0); solid boundary (includes =).
  5. y = |\(\color{blue}{2(2)-4}\)|+1 = |0|+\(\color{blue}{1 = 1}\); test: 0 < 1 → true, so (2, 0) is in the solution region.
  6. y ≥ |x| + 3 (or any y ≥ a|\(\color{blue}{x-h}\)|+3 with a > 0 and vertex at (0,3)).
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Free Graphing Absolute Value Inequalities Worksheet

Ready to practice on your own? Download our free Graphing Absolute Value Inequalities worksheet below, work through each problem at your own pace, and then check your answers. If a few give you trouble, scroll back up to the worked examples and try again, steady practice is the surest way to master Graphing Absolute Value Inequalities before a quiz or test.

Download Absolute Value Inequalities Worksheet

Frequently Asked Questions

How do you graph absolute value inequalities on a number line?

Solve the inequality first, then plot the endpoints. Use closed circles for ≤ or ≥ and open circles for < or >. For |x − 1| ≤ 2, the solution is −1 ≤ x ≤ 3, so put closed circles at −1 and 3 and shade the segment between them. A “greater than” inequality is shaded outward in both directions.

How do you graph absolute value inequalities on a coordinate plane?

Graph the boundary V first, then shade. For y ≥ |x − 2| − 1, the vertex is (2, −1), and the V is drawn solid because of the ≥ sign. Test a point such as (2, 0): 0 ≥ −1 is true, so shade the region above the V. For < or >, draw the V dashed.

What is an absolute value graph?

An absolute value graph is the V-shaped graph of a function like y = |x|. Its vertex is at the origin, and each side has a slope of 1 or −1. Changing the equation moves the V: y = |x + 3| shifts it 3 units left, and y = −|x| flips it upside down.

How do you solve and graph absolute value inequalities?

Isolate the absolute value, solve the matching compound inequality, then graph. For |x + 3| > 2, write x + 3 > 2 or x + 3 < −2, which gives x > −1 or x < −5. On a number line, draw open circles at −5 and −1 and shade left from −5 and right from −1.

How do you graph absolute value inequalities on a TI-84?

Press Y= and enter the boundary, for example abs(X − 2) − 1 (abs is under MATH, then NUM). Move the cursor to the far left of Y1 and press ENTER to cycle the line style to shade above or shade below, then press GRAPH. The shading does not show whether the boundary is included, so draw strict inequalities with a dashed boundary on paper.

How do you graph linear and absolute value inequalities?

Both use the same three steps: graph the boundary, choose solid or dashed, and shade the side that works. The only difference is the boundary shape: a straight line for something like y < 2x + 1, and a V for something like y < |x|. A test point such as (0, 1) tells you which side to shade.

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