Question

初一数学题，急急急急急急急急急急急急急急急

已知x-y-z=0,x-2y+z=0,则7y-x+2z分之5y+2x-z=
拜托各位了~谢谢

Answer 1

由x-y-z=0,x-2y+z=0，
得x=3z,y=2z
则(5y+2x-z)/(7y-x+2z)=(10z+6z-z)/(14z-3z+2z)=15/13

Answer 2

(1)+(2)得
2x-3y=0
∴y=2x/3
把y=2x/3代入(1)得
x-2x/3-z=0
∴z=x/3
把y=2x/3，z=x/3代入7y-x+2z分之5y+2x-z得
原式=(14x/3-x+2x/3)分之(10x/3+2x-x/3)
=13分之15
求采纳

Answer 3

x-y-z=0 ①
x-2y+z=0 ②

①+③得 2x-3y=0

2x=3y
②-①得 -y+2z=0
y=2z

(7y-x+2z)/(5y+2x-z)
将上面得到的等式代入
得 =（7y-1.5y+y)/(5y+3y-0.5y)
= (6.5y)/(7.5y)
=65/75
=13/15

Answer 4

答案应该是这个
15/13