Assuming the parabola is of the form y = ax^2 + bx + c or y= a(x-h)^2 - k, you look to the 'a' coefficient to determine whether the parabola has undergone a vertical "stretch" or "shrink." If a>1, then it's a stretch. If 0<a<1, then it's a shrink.
If, by the way, the a is negative, this test still works... just ignore the negative sign. So if for example a = -2/3, it's a shrink, but if a = -3 it's a stretch. (Incidentally, the negative sign makes the parabola "reflect" over the x-axis.)
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A parabola is NOT a point, it is the whole curve.
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.
To find the value of a in a parabola opening up or down subtract the y-value of the parabola at the vertex from the y-value of the point on the parabola that is one unit to the right of the vertex.
A parabola has a single focus point. There is a line running perpendicular to the axis of symmetry of the parabola called the directrix. A line running from the focus to a point on the parabola is going to have the same distance as from the point on the parabola to the closest point of the directrix. In theory you could look at a parabola as being an ellipse with one focus at infinity, but that really doesn't help any. ■
The vertex would be the point where both sides of the parabola meet.