如图,已知在△ABC中,DE∥BC,EF∥AB,AE=2CE,AB=6,BC=9.求:
(1)求BF和BD的长度.
(2)四边形BDEF的周长.
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There's many students in our school . ____of them ___ girls.
下列各例中,是利用红外线工作的是( )