解:(1)∵,, ∴. ∴Rt△CAO∽Rt△ABE.·························· 2分 ∴. ∴.∴.························· 3分 (2)由Rt△CAO∽Rt△ABE可知:,.··········· 4分 当0<<8时,. ∴.····························· 6分 当>8时,. ∴,(为负数,舍去). 当或时,.······················ 8分
(3)过M作MN⊥轴于N,则. 当MB∥OA时,,.··············· 9分 抛物线的顶点坐标为(5,).············· 10分 它的顶点在直线上移动. 直线交MB于点(5,2),交AB于点(5,1).············· 11分 ∴1<<2. ∴<<. 12分 |