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,z2、已知2X=5Y,求X/Y ,(X+Y)/Y ,(X-Y)/Y3、如图已知AD/BD=AE/EC=3/2,试求(1)AB/BD (2)EC/AC

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

1。(1)设X/2=Y/3+Z/4=K,则X=2K,Y=3K,Z=4K,
所以(X-Y+Z)/(X+Y+Z)=1/3
(2)因为2x+3yz=18,所以 4k+3*3k*4k=18 解方程求K,进一步求X、Y、Z
2。X/Y=5/2
(X+Y)/Y=X/Y+1=7/2
(X-Y)/Y=X/Y-1=3/2
3。没有图。

1、设X=2k、Y=3k、Z=4k. 则:
(1)(X-Y+Z)/(X+Y+Z)=3k/9k=1/3
(2)2x+3y-z=9k=18,k=2;故x=4,y=6,z=8
2、①由已知2X=5Y得 X=5Y/2, X/Y=5/2=2.5
② 同①理 (X+Y)/Y=3.5
③ 同①理 (X-Y)/Y=1.5

1.(1)令X/2=Y/3=Z/4=T,则X=2T,Y=3T,Z=4T,(X-Y+Z)/(X+Y+Z)=27T^2( T为任意数)
(2)将X=2T,Y=3T,Z=4T带入2x+3y z=18得,4T+36T^2=18,所以,T=(-1±√163)/18
2.X/Y =5/2,(X+Y)/Y =X/Y+1=3.5,,(X-Y)/Y=X/Y-1=1.5
3.没图

你把x=2.5y代进去算不就出来了

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....