∫ Function y=2x? ，y=-2x？ ，y= 1/2x？ The values of a and a are: a > 0, a < 0, a > 0;
The opening directions of parabola are: downward, downward and upward, that is, the opening directions are different;
By the function y=2x? ，y=-2x？ ，y= 1/2x？ Analytic formula of: the coordinates of vertices are all (0,0);
The characteristic of these three functions is that they are all symmetrical about y, and the vertex of parabola is the origin.
Extended data:
The specific expression of parabolic equation is y=ax? Geometric properties of +bx+c:
1、a≠0；
2, a > 0, parabolic opening upward; A < 0, parabolic opening downward;
3. Extreme point (vertex): (-b/2a, 4ac-b? /4a)；
4、δ= b？ -4ac, δ > 0, where the image intersects the X axis at two points; δ = 0, the image intersects with the X axis at a point: δ < 0, the image does not intersect with the X axis;
5. When the symmetry axis (vertex) is on the left side of the Y axis, the symbols of A and B are the same; When the axis of symmetry (vertex) is on the right side of Y axis, the symbols of A and B are different; When the axis of symmetry (vertex) is on the Y axis, b=0, and when the vertex of parabola is at the origin, b=c=0.
6. when x=0, the value of c can be judged by the intersection with the y axis, that is, if the parabola intersects with the y axis as a positive semi-axis, then c > 0；; If the y axis of the parabola is the negative semi-axis, then C < 0.
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