若丨x+y-3丨+根号2x-y=0,则x-y=

若丨x+y-3丨+根号2x-y=0,则x-y=
若丨x+y-3丨+根号2x-y=0,则x-y=

若丨x+y-3丨+根号2x-y=0,则x-y=
因为丨x+y-3丨≥0,根号2x-y≥0,而丨x+y-3丨+根号2x-y=0
所以x+y-3=0,2x-y=0
解得x=1,y=2
则x-y=-1

丨x+y-3丨+根号2x-y=0
丨x+y-3丨>=0
根号2x-y>=0
x+y=3
2x-y=0
3x=3
x=1
y=2
x-y=1-2=-1

x+y-3=0
2x-y=0
x=1 y=2
x-y=-1