1、已知X/2=Y/3=Z/4,(1)求（X-Y+Z)/(X+Y+Z) (2)若2x+3y z=18,求x,y,z
问题描述：
1、已知X/2=Y/3=Z/4,(1)求（X-Y+Z)/(X+Y+Z) (2)若2x+3y z=18,求x,y,z
2、已知2X=5Y,求X/Y ,(X+Y)/Y ,(X-Y)/Y
3、如图已知AD/BD=AE/EC=3/2,试求（1）AB/BD (2)EC/AC
答
1.设a＝X/2=Y/3=Z/4,则：X=2a；Y=3a；Z=4a代入得：(1)（X-Y+Z)/(X+Y+Z)=3a/(9a)＝1/3(2)2x+3y-z＝9a=18,a=2；故x=4,y=6,z=82.2X=5Y.x/y=5/2＝2.5x=2.5y(x+y)/y＝3.5Y/Y=3.5(x-y)/y=1.5y/y＝1.53.没有图....