Graph of x² (the parabola y = x²)
The graph of y = x² is the simplest parabola: a symmetric U with its lowest point, the vertex, at the origin. Every quadratic function is this same shape, stretched, flipped or moved.
Key features
- Domain
- All real numbers
- Range
- y ≥ 0
- Vertex
- (0, 0), a minimum
- Axis of symmetry
- x = 0
- Opens
- Upward
- Symmetry
- Even: (−x)² = x²
- Focus and directrix
- Focus (0, 1/4), directrix y = −1/4
- y-intercept
- None
- Derivative
- 2x
- Antiderivative
- 13x3+C
Derivative and antiderivative from the calculator’s algebra system. Domain, range and asymptotes are stated for real x.
What the graph of x² looks like
Squaring makes negative and positive inputs give the same output, so the graph is a mirror image of itself across the y-axis: (−2, 4) matches (2, 4). The only point where the output is zero is the vertex, (0, 0).
The parabola gets steeper as it climbs. Its slope is 2x: zero at the vertex, 2 at x = 1, 4 at x = 2. The heights 1, 4, 9, 16 grow by the odd numbers 3, 5, 7, which is a quick check when plotting.
Geometrically, a parabola is the set of points the same distance from a fixed point (the focus) and a fixed line (the directrix). For y = x² those are (0, 1/4) and y = −1/4, which is why parabolic dishes focus incoming parallel rays.
Points of interest
Found numerically to about twelve digits in the window −5 ≤ x ≤ 5, 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
- None in this window
Table of values
A few points to plot, with exact values where they are simple.
| x | y = x² |
|---|---|
| −3 | 9 |
| −2 | 4 |
| −1 | 1 |
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
How to graph x² by hand
- 1Plot the vertex (0, 0).
- 2Plot (1, 1) and (−1, 1), then (2, 4) and (−2, 4), then (3, 9) and (−3, 9).
- 3Draw a smooth U through the points. The bottom should be rounded, not a V.
Transformations
How the graph moves when you change the formula. The original is x² in blue.
y = (x - 2)^2 + 1Vertex form a(x − h)² + k with h = 2, k = 1: the vertex moves to (2, 1).y = -0.5x^2a = −0.5: flipped upside down and widened.y = 3x^2a = 3: narrower, climbing three times as fast.
Common mistakes
- Drawing a V with a sharp point at the vertex. A parabola is smooth everywhere.
- Shifting the wrong way: (x − 2)² moves the graph right by 2, not left.
Where it shows up
- Projectile motion: height against time under gravity is a downward parabola.
- Area: the area of a square of side x is x².
- Parabolic reflectors in satellite dishes, car headlights and telescopes.
Frequently asked questions
What is the vertex of y = x²?
What is the range of x²?
What is the axis of symmetry of y = x²?
How do I graph y = a(x − h)² + k?
Related graphs
An S-shape through the origin, flat at its inflection point.
Starts at the origin; half of a sideways parabola.
A V with its vertex at the origin, slopes ±1.
A straight line: slope m, y-intercept b.
Always positive; both branches above the x-axis.
The bell curve: peak (0, 1), area √π.
Change the window, add sliders for a, b, h and k, trace the curve with your keyboard, or overlay its derivative.