A--------E----D---B-------F------------C
BD=1/4AB=1/2EB EB=2BD
BD=1/5CD=2/5DF DF=5/2BD=2.5BD
EF=EB+DF-BD=2BD+2.5BD-BD=3.5BD=7
所以BD=2
所以AB=8 CD=10
A--------E----D---B-------F------------C
BD=1/4AB=1/2EB EB=2BD
BD=1/5CD=2/5DF DF=5/2BD=2.5BD
EF=EB+DF-BD=2BD+2.5BD-BD=3.5BD=7
所以BD=2
所以AB=8 CD=10