题目内容
(本题满分12分,每小题满分各6分)已知:直角坐标系xoy中,将直线沿y轴向下平移3个单位长度后恰好经过B(-3,0)及y轴上的C点.若抛物线与轴交于A,B两点(点A在点B的右侧),且经过点C,(1)求直线及抛物线的解析式;(2)设抛物线的顶点为,点在抛物线的对称轴上,且,求点的坐标;
⑴ 沿轴向下平移3个单位长度后经过轴上的点,
∴C(0,-3)…(1分)
设直线的解析式为.···················· (1分)
∵ B(-3 ,0) 在直线上,∴ -3k-3="0 " 解得.
∴直线的解析式为.····················· (1分)
抛物线过点,
∴··························· (2分)
解得 ∴ 抛物线的解析式为. ········ (1分)
⑵ 由.可得D(-2,1) ,A(-1,0).………………………………(1分)
,,,.可得是等腰直角三角形.
,.······················· (1分)
设抛物线对称轴与轴交于点,∴AF=AB="1 " .
过点作于点..
可得,.····················· (1分)
在与中,,,
.··························· (1分)
,.解得.
点在抛物线的对称轴上, 点的坐标为或.········ (2分)解析:
略
∴C(0,-3)…(1分)
设直线的解析式为.···················· (1分)
∵ B(-3 ,0) 在直线上,∴ -3k-3="0 " 解得.
∴直线的解析式为.····················· (1分)
抛物线过点,
∴··························· (2分)
解得 ∴ 抛物线的解析式为. ········ (1分)
⑵ 由.可得D(-2,1) ,A(-1,0).………………………………(1分)
,,,.可得是等腰直角三角形.
,.······················· (1分)
设抛物线对称轴与轴交于点,∴AF=AB="1 " .
过点作于点..
可得,.····················· (1分)
在与中,,,
.··························· (1分)
,.解得.
点在抛物线的对称轴上, 点的坐标为或.········ (2分)解析:
略
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