已知x,y满足等式3x+y/2=9x+2y/4=1, 求代数式x+2y+1/2x-3y+7的值

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已知x,y满足等式3x+y/2=9x+2y/4=1, 求代数式x+2y+1/2x-3y+7的值
已知x,y满足等式3x+y/2=9x+2y/4=1, 求代数式x+2y+1/2x-3y+7的值

已知x,y满足等式3x+y/2=9x+2y/4=1, 求代数式x+2y+1/2x-3y+7的值
又3x+y/2=9x+2y/4=1
得x=0,y=2
带入x+2y+1/2x-3y+7得
x+2y+1/2x-3y+7=(0+4+1)/(0-6+7)=5

∵2x+y/2=5x+4y/4=1
∴2x+y=2
5x+4y=4
∴x=4/3
y=-2/3
∴x+2y+1/2x-3y+7
=(4/3-4/3+1)/(8/3+2+7)
=1/(35/3)
=3/35