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)=53x+y/2=9x+2y/4=1怎么解3x+y/2=19x+2y/4=1两式相减6x=0∴x=0∴0+y/2=1∴y=2