Free graphing resources · Original practice

Graphing absolute value functions.
Find the corner, then the arms.

Plot four functions in y=a|x-h|+k. Identify each vertex and symmetry line, calculate sample values and compare upward, downward and wider V shapes.

4 absolute-value cases.
Vertex + table + answer.

A graph, a task and a worked check

Plot four functions in y=a|x-h|+k. Identify each vertex and symmetry line, calculate sample values and compare upward, downward and wider V shapes.

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Choose a specific case

CaseFocus
AV01A centered V
AV02A shifted V
AV03A reflected V
AV04A wider V

All examples use original fictional data and coordinate units. They are practice material, not measured classroom results, published questions or evidence about real people.

Check the first case

AV01: A centered V

CheckWorked result
1Vertex (0,0); axis x=0.
2(-3,3); (-1,1); (0,0); (1,1); (3,3)
3Opens up.

The first case shows the checking pattern. Individual answer files contain the completed graph and result for every case.

Work through the graph

  1. Locating the Vertex Precisely

    Begin by identifying the vertex coordinates h and k from the function definition y equals a absolute value of x minus h plus k. For the centered V case, the vertex is at zero zero. For the shifted V, it is at two negative one. Mark this point clearly on your grid. Do not rely on physical ruler measurements to find this spot. Instead, use the listed coordinates provided in the reference PDF. This ensures the sharp corner aligns exactly with the mathematical definition. The vertex serves as the anchor for all subsequent plotting steps. Accurate placement here prevents distortion in the rest of the graph. Verify the coordinates against the supplied values before proceeding to the next step.

  2. Plotting Symmetric Input Values

    Use the table of symmetric inputs around the vertex h to calculate y values. For the reflected V case with vertex at negative one three, use inputs negative four, negative two, negative one, zero, and two. Calculate each output using the function rule. Plot these points on the coordinate plane. Connect the points with straight lines to form the V shape. Ensure the lines meet at a sharp corner at the vertex. Do not smooth the corner. The symmetry of the inputs ensures the graph balances correctly around the vertical axis of symmetry. Check your plotted points against the answer PDF to confirm accuracy. This method relies on calculation, not physical estimation.

  3. Applying the Scale Factor

    Adjust the width of the V by applying the coefficient a. For the wider V case, use a equals one half. This value stretches the graph vertically compared to the standard V. Calculate the y values using this factor. The vertex remains at one negative two. The inputs are negative two, zero, one, two, and four. Plot these calculated points. The graph will appear broader than the standard case. Do not use a physical ruler to estimate the width. Rely on the calculated coordinates. The negative sign in other cases flips the graph downward. Verify the shape matches the reference image. The scale factor directly controls the steepness of the lines.

Checks that catch common errors

Watch forCheck instead
Using a physical ruler to measure distances on the printed page to determine the vertex location.Use the digital coordinates provided in the reference PDF to locate the vertex exactly on the grid.
Smoothing the corner at the vertex to make the graph look like a curve.Plot a sharp corner at the vertex by connecting the straight lines directly at the calculated point.
Assuming the graph width is standard when the coefficient a is one half.Apply the scale factor a equals one half to stretch the graph vertically, making it wider than the standard case.

Keep the labels and margins readable

Choose the PDF that matches your paper. Print at Actual size / 100% and turn off Fit, Shrink and browser headers. SVG is editable but an editor can rescale it; the PDF is the simpler print route. Physical printer, classroom and curriculum tests have not been completed.

Useful answers

Why is the vertex not the opposite sign of h?

Match the expression with x-h. In |x-2| the vertex x-coordinate is 2; in |x+2| it is -2.

Does a negative a change the vertex?

No. It changes the opening direction and makes the vertex a maximum, but h and k still locate the corner.

Should I join the V with a curve?

No. Plot the samples, then use two straight arms with the correct slopes.

Are the answer files and editable graphs free?

Yes. The individual student, reference and answer files plus collection packs are free without signup. Credit Zumola under CC BY 4.0 when sharing or adapting.

Keep practicing

Further reading: OpenStax: absolute value functions. The diagrams, datasets and exercises here are original Zumola work.

More ways to practice

Endpoint and inequality boundary checks

For any absolute value graph y = a|x - h| + k, the vertex is at (h, k). The two linear pieces have slopes a and -a. When graphing an inequality such as y < a|x - h| + k, first graph the boundary y = a|x - h| + k. Use a dashed boundary if the inequality is strict (< or >) and a solid boundary if it includes equality (≤ or ≥). Then test one point not on the boundary to decide which region to shade.

A common error is shading the wrong side because the test point lies on the boundary or because the inequality symbol was misread. Choose a test point clearly inside one region, such as the vertex shifted vertically by one unit, and substitute it into the original inequality. If the statement is true, shade that region; if false, shade the other side.

Also check the domain and range. The domain of any absolute value function of this form is all real numbers. The range depends on the sign of a: if a > 0, the range is y ≥ k; if a < 0, the range is y ≤ k. For inequalities, the shaded region may extend beyond these bounds, so state the boundary's range separately from the shaded set.

  1. Identify h, k, and a from the equation; plot the vertex (h, k).
  2. Use the slope a to plot one point to the right of the vertex, and -a to plot one point to the left.
  3. Draw the V-shaped boundary with a dashed line for strict inequalities or a solid line for inclusive inequalities.
  4. Choose a test point not on the boundary and substitute it into the inequality.
  5. Shade the region where the inequality is true, and label the boundary equation.

New worked example: inequality with a shifted vertex

Consider the inequality y ≤ 2|x - 1| - 3. The boundary is y = 2|x - 1| - 3, with vertex (1, -3) and slopes 2 and -2. Because the inequality includes equality (≤), draw a solid V. To decide shading, test the point (1, 0), which is above the vertex. Substitute: 0 ≤ 2|1 - 1| - 3 = -3, which is false. Therefore shade the region below the V, not above it.

Verify with another point: (0, -1). Left side: -1. Right side: 2|0 - 1| - 3 = 2(1) - 3 = -1. The statement -1 ≤ -1 is true, so (0, -1) lies on the boundary and should be included. A point just below the boundary, such as (0, -2), gives -2 ≤ -1, true, confirming the shaded region is below.

This example also exposes a frequent mistake: assuming the shaded region is always above the V. The test point method prevents that error. Record the test point and its substitution on the worksheet so the reasoning can be checked independently.

  1. Write the boundary equation and identify vertex (1, -3).
  2. Plot the vertex and use slope 2 to reach (2, -1) and slope -2 to reach (0, -1).
  3. Draw a solid V through these points.
  4. Test (1, 0): 0 ≤ -3 is false, so shade below the V.
  5. Confirm with (0, -2): -2 ≤ -1 is true, so the lower region is correct.

Diagnostic checks for independent verification

After graphing, verify three independent features: the vertex coordinates, one point on each branch, and the direction of opening. For y = a|x - h| + k, the vertex must satisfy the equation exactly. Substitute x = h and confirm y = k. Then choose x = h + 1 and x = h - 1; both substitutions give y = a|1| + k = k + a, so the two points are symmetric about x = h and their y-value is k + a. If a is negative, this value is below k, which confirms the downward opening.

Check intercepts only when they exist. The y-intercept is found by setting x = 0: y = a| -h| + k = a|h| + k. The x-intercepts require solving a|x - h| + k = 0, which has solutions only if -k/a ≥ 0. If no real solution exists, state that the graph has no x-intercept rather than forcing one.

Finally, confirm that the graph is a function: it must pass the vertical line test. Absolute value graphs of this form always do, but inequality regions may not represent functions. Label the boundary and shaded region clearly so the reader can distinguish the function from the solution set.

  1. Substitute x = h into the equation and confirm the output is k.
  2. Plot points at x = h + 1 and x = h - 1; check they are symmetric about x = h and both equal k + a.
  3. Calculate the y-intercept by substituting x = 0.
  4. Solve for x-intercepts only if the equation yields real values; otherwise state none.
  5. For inequalities, verify shading with at least one test point and label the boundary type.

Try this example

Graph the inequality y > |x + 2| - 1 and determine the shaded region.

Show the worked explanation

The boundary is y = |x + 2| - 1, with vertex (-2, -1) and slopes 1 and -1. Since the inequality is strict (>), draw a dashed V. Test the point (-2, 0): 0 > |0| - 1 = -1 is true, so shade above the V. Check (-2, -2): -2 > -1 is false, confirming the region below is excluded. The boundary is not part of the solution.

Common mistakes

Check your work

Questions before you start

How do I know which side to shade for an absolute value inequality?

Graph the boundary first, then test one point not on the boundary. If the test point makes the inequality true, shade the region containing that point; otherwise shade the other region.

Can an absolute value graph have no x-intercepts?

Yes. For y = a|x - h| + k, x-intercepts exist only when -k/a is greater than or equal to zero. If it is negative, the graph does not cross the x-axis.

What is the range of y = -2|x + 1| + 4?

Because a = -2 is negative, the graph opens downward with vertex (-1, 4). The range is y ≤ 4.

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