题目内容
(本题满分9分)已知如图,矩形的长,宽,将沿翻折得.
(1)填空:度,点坐标为( , );
(2)若两点在抛物线上,求的值,并说明点在此抛物线上;
(3)在(2)中的抛物线段(不包括点)上,是否存在一点,使得四边形的面积最大?若存在,求出这个最大值及此时点的坐标;若不存在,请说明理由.
解:(1), ················································ 4分
(2)点,在抛物线上,
······················································ 2分
抛物线的解析式为 ······································ 1分
点坐标为
点在此抛物线上. ····························································· 1分
(3)假设存在这样的点,使得四边形的面积最大.
面积为定值,
要使四边形的面积最大,只需使的面积最大.
过点作轴分别交和轴于和,过点作轴交于.
设,
························································ 2分
,有最大值.
当时,的最大值是,
四边形的面积的最大值为. ··································· 1分
此时点的坐标为. ·················································· 1分
所以存在这样的点,使得四边形的面积最大,其最大值为.
解析
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