已知2x+3y+z=130,3x+5y+z=180,试求x+2y/x+y+z的值要正确的!

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已知2x+3y+z=130,3x+5y+z=180,试求x+2y/x+y+z的值要正确的!已知2x+3y+z=130,3x+5y+z=180,试求x+2y/x+y+z的值要正确的!已知2x+3y+z=

已知2x+3y+z=130,3x+5y+z=180,试求x+2y/x+y+z的值要正确的!
已知2x+3y+z=130,3x+5y+z=180,试求x+2y/x+y+z的值要正确的!

已知2x+3y+z=130,3x+5y+z=180,试求x+2y/x+y+z的值要正确的!
2x+3y+z=130（1）
3x+5y+z=180（2）
（2）-（1）得 x+2y=50
x=50-2y代入（1）得
100-4y+3y+z=130
z=y+30
∴x+2y/x+y+z
=(50-2y+2y)/(50-2y+y+y+30)
=50/80
=5/8

2x+3y+z=130，①
3x+5y+z=180，②
②-①=x+2y=50,③
①-③=x+y+z=80④
③/④=x+2y/x+y+z=5/8

x+2y/x+y+z=50/80=5/8
后一式子减前一式子得x+2Y=50
前一式子减x+2Y=50得x+y+z=80

x+2y=（3x+5y+z）-（2x+3y+z）=180-130=50
x+y+z=（2x+3y+z）-（x+2y）=130-50=80
所以x+2y/x+y+z = 50/80 = 5/8

2x+3y+z=130，3x+5y+z=180
两式相减
x+2y=50带入2x+3y+z=130
x+y+z=80

x+2y/x+y+z=50/80=5/8

因为(3x+5y+z)-(2x+3y+z)=x+2y=180-130=50
(2x+3y+z)-(x+2y)=x+y+z=130-50=80
所以(x+2y)/(x+y+z)=50/80=5/8

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已知2x+3y+z=130,3x+5y+z=180,试求x+2y/x+y+z的值 要正确的!

已知2x+3y+z=130,3x+5y+z=180,试求x+2y/x+y+z的值要正确的!