在梯形ABCD中,AB‖CD,AB=a,CD=b,两腰延长线交于点M,过M作DC的平行线,交AC、BD延长线于E,EF等于( )A.ab/a-b B.2ab/a-b C.a/a+b D.2ab/a+b

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在梯形ABCD中,AB‖CD,AB=a,CD=b,两腰延长线交于点M,过M作DC的平行线,交AC、BD延长线于E,EF等于()A.ab/a-bB.2ab/a-bC.a/a+bD.2ab/a+b在梯形A

在梯形ABCD中,AB‖CD,AB=a,CD=b,两腰延长线交于点M,过M作DC的平行线,交AC、BD延长线于E,EF等于( )A.ab/a-b B.2ab/a-b C.a/a+b D.2ab/a+b
在梯形ABCD中,AB‖CD,AB=a,CD=b,两腰延长线交于点M,过M作DC的平行线,交AC、BD延长线于E,EF等于( )
A.ab/a-b B.2ab/a-b C.a/a+b D.2ab/a+b

在梯形ABCD中,AB‖CD,AB=a,CD=b,两腰延长线交于点M,过M作DC的平行线,交AC、BD延长线于E,EF等于( )A.ab/a-b B.2ab/a-b C.a/a+b D.2ab/a+b
CD/EM=BD/BM=AC/AM=CD/MF,EM=MF,EF=2EM
DM/BM=CD/AB,1-DM/BM=1-CD/AB,(BM-DM)/BM=(AB-CD)/AB,BD/BM=(a-b)/a
CD/EM=BD/BM=CD/0.5EF=2b/EF=(a-b)/a
EF=2ab/(a-b)
选B