Absolute value graph: y = |x|
The absolute value graph is a V. For x ≥ 0 it is the line y = x, for x < 0 it is the line y = −x, and the two halves meet at a sharp corner at the origin.
Key features
- Domain
- All real numbers
- Range
- y ≥ 0
- Vertex
- (0, 0), a minimum
- Slopes
- −1 for x < 0, +1 for x > 0
- Piecewise form
- y = x if x ≥ 0, y = −x if x < 0
- Symmetry
- Even: |−x| = |x|
- Differentiability
- Not differentiable at x = 0 (a corner)
- y-intercept
- None
- Derivative
- sign(x)
- Antiderivative
- x|x|2+C
Derivative and antiderivative from the calculator’s algebra system. Domain, range and asymptotes are stated for real x.
What the graph of |x| looks like
The absolute value measures distance from zero, so it is never negative: |−3| = |3| = 3. The graph keeps the right half of the line y = x and reflects the left half up above the x-axis.
The corner at the origin is where the slope jumps from −1 to +1. There is no single tangent line there, which is why |x| is the standard example of a continuous function that is not differentiable.
Absolute value graphs appear wherever a quantity is a distance: |x − 3| is the distance from x to 3, and its graph is the same V moved so its vertex sits at x = 3.
Points of interest
Found numerically to about twelve digits in the window −6 ≤ x ≤ 6, then shown in exact form where one exists.
- x-intercepts (roots)
- x = 0
- Local maxima
- None in this window
- Local minima
- None in this window
- Inflection points
- (−6, 6), (−5.997, 5.997), (−5.994, 5.994), (−5.991, 5.991), (−5.988, 5.988), (−5.985, 5.985) … (4001 in view)
Table of values
A few points to plot, with exact values where they are simple.
| x | y = |x| |
|---|---|
| −3 | 3 |
| −2 | 2 |
| −1 | 1 |
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 3 |
How to graph |x| by hand
- 1Plot the vertex (0, 0).
- 2Plot (1, 1), (2, 2), (3, 3) to the right and (−1, 1), (−2, 2), (−3, 3) to the left.
- 3Join each side with a straight ray, meeting in a sharp point at the origin.
Transformations
How the graph moves when you change the formula. The original is |x| in blue.
y = abs(x - 2) + 1Vertex moved to (2, 1).y = -2abs(x)Flipped upside down and twice as steep.y = abs(x^2 - 4)Absolute value of a parabola: the part below the axis is reflected up, making a W.
Common mistakes
- Rounding the vertex. |x| has a sharp corner, unlike a parabola.
- Moving the vertex the wrong way: |x − 2| has its vertex at x = 2.
Frequently asked questions
What does the absolute value graph look like?
What is the range of y = |x|?
How do I find the vertex of y = a|x − h| + k?
Is |x| differentiable?
Related graphs
The basic parabola: vertex (0, 0), opens upward.
A straight line: slope m, y-intercept b.
Starts at the origin; half of a sideways parabola.
A staircase: jumps of 1 at every integer.
A hyperbola with asymptotes along both axes.
An S-shape through the origin, flat at its inflection point.
Change the window, add sliders for a, b, h and k, trace the curve with your keyboard, or overlay its derivative.