AB=CD=x,BM=y,NB=y+4.5,MD=12-y因为三角形NEF∽三角形NAB,三角形MEF∽三角形MCD所以EF/AB=NF/NB,EF/CD=MF/MD即1.8/X=3/(y+4.5),1.8/x=1.5/(12-y)得3/(y+4.5)=1.5/(12-y),y=6.5y带入1.8/x=1.5/(12-y),x=6.6
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