Figure 1. |
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Above we have a parabola with its vertex and axis of symmetry labeled.

Equation of a Parabola |
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The standard form of an equation of a parabola with vertex (h, k) Axis of Symmetry x = h is written as: If a > 0, then k is the minimum, and the parabola opens upward. If a < 0, then k is the maximum, and the parabola opens downward. |

Below, two parabolas are graphed:

Figure 2. |
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Figure 3. |
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Each parabola has a focus, and a directrix.

Figure 4. |
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For any given point, the distance to the focus is equal to the distance to the directrix.

The Latus Rectum specifies the width of the parabola:

Figure 5. |
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The smaller a is, the wider the parabola is.