抛物线y=ax2+2x+c的顶点坐标为(2,3),则a= _ ,c= _ .
问题描述:
抛物线y=ax2+2x+c的顶点坐标为(2,3),则a= ___ ,c= ___ .
答
∵y=ax2+2x+c,
∴-
=-b 2a
=-2 2a
,1 a
=4ac-b2
4a
=4ac-4 4a
,ac-1 a
∵顶点坐标为(2,3),
∴
,
-
=21 a
=3ac-1 a
解得
,
a=-
1 2 c=1
故答案为-
,1.1 2