已知二次函數(shù)的圖象經(jīng)過(guò)點(diǎn)(0,-4),且當(dāng)x=2時(shí),有最大值是-2,求該二次函數(shù)的關(guān)系式.
由二次函數(shù)當(dāng)x=2時(shí),有最大值是-2,得到頂點(diǎn)坐標(biāo)為(2,-2),
設(shè)二次函數(shù)解析式為y=a(x-2)
2-2(a≠0),
將x=0,y=-4代入得:-4=4a-2,
解得:a=-
,
則二次函數(shù)解析式為y=-
(x-2)
2-2=-
x
2+2x-4.