① General formula: y = ax 2; +bx+c(a, b, c are constants, a≠0)

② Vertex [vertex P(h, k) of parabola]: y = a (x-h) 2+k.

③ Intersection point [only applicable to parabolas with intersection points A(x 1 0) and B(x2, 0) with the X axis ]: y = a (x-x 1) (x-x2).

The above three forms can be converted as follows:

Relationship between (1) General Formula and Vertex Type

For the quadratic function y=ax+bx+c, its vertex coordinates are (-b/2a), (4ac-b2)/4a), that is.

h=-b/2a=(x 1+x2)/2

k=(4ac-b？ )/4a

② Relationship between general formula and intersection point

x 1，x2=[-b √(b？ -4ac)]/2a (that is, the formula for finding the root of a quadratic equation with one variable)