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directrix
Vertex (APEX)
just did it, swear
It is the vertex of the parabola.
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This extreme point on the parabola is called the vertex. In math. a parabola is a U-shaped curve with a directrix, which is a fixed straight line.
The vertex -- the closest point on the parabola to the directrix.
The line of symmetry located on a parabola is right down the center. A parabola is a U shape. Depending on the direction of the parabola it either has a x axis of symmetry or y axis of symmetry. You should have two equal sides of the parabola.
midpoint
Halfway between North America and Europe.
Parallel to the y-axis, going through the highest/lowest point of the parabola (if the parabola is negative/positive, respectively).
the Equator
The Equator.
Halfway between Baltimore MD and Washington DC.
Chicago, Illinois and Atlanta, Georgia are 719 miles apart. A city located halfway between them would be Bonnieville in Kentucky.