复数的虚部为 .
如图所示,已知DE∥BC,BF∶EF=3∶2,则AC∶AE=________,AD∶DB=________.
如图所示,l1∥l2∥l3,若CH=4.5 cm,AG=3 cm,BG=5 cm,EF=12.9 cm,则DH=________,EK=________.
如图所示,已知a∥b,=,=3,则AE∶EC=________.
如图所示,在△ABC中,MN∥DE∥BC,若AE∶EC=7∶3,则DB∶AB的值为________.
如图,在△ABC中,点E是AB的中点,EF∥BD,EG∥AC交BD于点G,CD=AD,若EG=5 cm,则AC=________cm;若BD=20 cm,则EF=________cm.