23.解:(1)该商场销售家电的总收益为(元)·························· 2分
(2)依题意可设
,
有
,
,
解得.
所以,
.··········································································· 3分
(3)
政府应将每台补贴款额定为100元,总收益有最大值.
其最大值为元.································································································ 3分
22.解:(1)设一次购物用6个袋的人数为人,则依条件有
,则记者共调查了
人.··················· 2分
(2)这100位顾客平均一次购物使用购物袋的平均数为
(个)
个.
估计这三大商业集团为顾客每天提供18000个塑料购物袋.·········································· 3分
(3)74%;25;
多数人环保意识增强,(只要是涉及环保节能等方面思想向上的即可).····················· 3分
21.解:在
中,
∵,
∴.······················ 3分
在中,
∵,
∴.········································································ 3分
∴.························································································· 2分
答:发射架高为25m.
20.解:(1)当时,函数为
,它的图象显然与
轴
只有一个交点.·································································································· 2分
当时,依题意得方程
有两等实数根.
,
.
当
或
时函数图象与
轴恰有一个交点.··················································· 2分
(2)依题意有分类讨论解得
或
.
当或
时,抛物线顶点始终在
轴上方.······················································· 4分
19.解:原式·························································· 4分
.···································································································· 2分
当时,原式
.························································································ 1分
18.证明:
,
,
.····················································· 2分
又,
,即
.························ 2分
又,
.
.·············································································································· 3分
17.解:原式··········································································· 4分
········································································································ 3分
11. 12.60° 13.3∶5 14.
15.
16.
25.(本小题满分10分)
正方形在如图所示的平面直角坐标系中,
在
轴正半轴上,
在
轴的负半轴上,
交
轴正半轴于
交
轴负半轴于
,
,抛物线
过
三点.
(1)求抛物线的解析式;(3分)
(2)是抛物线上
间的一点,过
点作平行于
轴的直线交边
于
,交
所在直线于
,若
,则判断四边形
的形状;(3分)
(3)在射线上是否存在动点
,在射线
上是否存在动点
,使得
且
,若存在,请给予严格证明,若不存在,请说明理由.(4分)
黄石市2009年初中毕业生学业考试
数学答案及评分标准
24.(本小题满分9分)
如图,中,点
是边
上一个动点,过
作直线
,设
交
的平分线于点
,交
的外角平分线于点
.
(1)探究:线段与
的数量关系并加以证明;(3分)
(2)当点在边
上运动时,四边形
会是菱形吗?若是,请证明,若不是,则说明理由;(3分)
(3)当点运动到何处,且
满足什么条件时,四边形
是正方形?(3分)
湖北省互联网违法和不良信息举报平台 | 网上有害信息举报专区 | 电信诈骗举报专区 | 涉历史虚无主义有害信息举报专区 | 涉企侵权举报专区
违法和不良信息举报电话:027-86699610 举报邮箱:58377363@163.com