.(6分) 已知二次函数

的图象与y轴交于点A(0,-6),与x轴的一个交点坐标是B(-2,0).
(1)求二次函数的关系式,并写出顶点坐标;
(2)将二次函数图象沿x轴向左平移

个单位长度,求所得图象对应的函数关系式.
解:(1)把A(O,-6)代入y=x
2+bx+c求得

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把B(-2,0)代入y=x
2+bx-6求得

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所以

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所以顶点坐标

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(2)二次函数图象沿x轴向左平移

个单位长度得:

··············(6分)解析:
略