核心知识梳理1.二次函数的图象(抛物线)和性质,如表1.表12.二次函数图象(抛物线)的三要素:开口方向、对称轴、顶点.(1)对于抛物线y=ax~2+bx+c,a的符号决定抛物线的开口方向,|a|相等,抛物线的开口大小、形状相同;|a|越大,抛物线开口越小.(2)抛物线的对称轴是平行(或重合)于y轴的直线.顶点决定抛物线的位置.3.与抛物线相关的交点:(1)抛物线y=ax~2+bx+c与y轴的交点为(0,c). Core Knowledge 1. Image (parabola) and properties of quadratic functions, as shown in Table 1. Table 12. Three elements of quadratic function image (parabola): opening direction, axis of symmetry, vertex (1) For parabola y = ax ~ 2 + bx + c, the sign of a determines the parabola’s opening direction, | a | is equal, the parabola’s opening size is the same, the shape is the same; | a | the bigger the parabola’s opening is. (2) Parallel (or coincident) with the y-axis of a straight line. Vertices determine the position of the parabola .3 parabola-related intersection points: (1) parabola y = ax ~ 2 + bx + c and y axis intersection point (0, c).