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= ___ .

∵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),
-
1
a
=2
ac-1
a
=3

解得
a=-
1
2
c=1

故答案为-
1
2
,1.