抛物线y=ax2+bx+c的顶点坐标为(3,-2),与x轴两交点的距离为4,求抛物线的解析式.

问题描述:

抛物线y=ax2+bx+c的顶点坐标为(3,-2),与x轴两交点的距离为4,求抛物线的解析式.

根据题意得:-

b
2a
=3,
4ac−b2
4a
=-2,|x1-x2|=
(x1+x2)2−4x1x2
=
(−
b
a
)2
4c
a
=4,
联立三式解得:a=
1
2
,b=-3,c=
5
2

则抛物线解析式为y=
1
2
x2-3x+
5
2