摘要：已知:如图所示的两条抛物线的解析式分别是 .(其中为常数.且)． (1)请写出三条与上述抛物线有关的不同类型的结论, (2)当时.设与轴分别交于两点(在的左边).与轴分别交于两点(在的左边).观察四点坐标.请写出一个你所得到的正确结论.并说明理由, (3)设上述两条抛物线相交于两点.直线都垂直于轴.分别经过两点.在直线之间.且与两条抛物线分别交于两点.求线段的最大值． (1)解:答案不唯一.只要合理均可．例如: ①抛物线开口向下.或抛物线开口向上, ②抛物线的对称轴是.或抛物线的对称轴是, ③抛物线经过点.或抛物线经过点, ④抛物线与的形状相同.但开口方向相反, ⑤抛物线与都与轴有两个交点, ⑥抛物线经过点或抛物线经过点, 等等．························································································································ 3分 (2)当时..令. 解得．····························································································· 4分 .令.解得．························ 5分 ①点与点对称.点与点对称, ②四点横坐标的代数和为0, ③(或)．··········································· 6分 (3). 抛物线开口向下.抛物线开口向上．········· 7分 根据题意.得．············ 8分 当时.的最大值是2．········································································· 9分 说明:1．第(1)问每写对一条得1分,

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