发布时间 : 星期二 文章2018-2019学年上海市杨浦区初三数学第一学期期末质量调研(参考答案)2019.01更新完毕开始阅读28cf161aa88271fe910ef12d2af90242a995ab69
∵AD//BC，∴ADAE，即318-3x. x.∴
==BF=BFEBxBF6-x∵△AEF的面积为3，∴1. 18-3x鬃x=32x······························································································· （1分） ∴x=4. ·
∵AD=3，AB⊥AD，∴DE=5. ∵DE1，∴DC=10.
DC=2∵DF⊥DC，∴
S1. ·························································VDCE=2创510=25当点E在边AB延长线上，设AE=y，
∵AD//BC，∴ADAE，即3y.∴3y-18. BF=EBBF=y-6BF=y∵△AEF的面积为3，∴1.∴y=8. ······································2鬃y3y-18···y=3∵AD=3，AB⊥AD，∴DE=73.
联结CE，作CH⊥AD交AD的延长线于点H，同（1）可得DE1.
·················DC=2∴DC=273 ∵DF⊥DC，∴
S1. ················································VDCE=2创73273=73综上，当△AEF的面积为3时，△DCE的面积为25或73.
1分） 1分）
1分） 1分） （ （ （ （