∵2x+4y-xy=0
∴y=2x/(x-4)
x+y
=2x/(x-4) +x
=2+8/(x-4) +(x-4) +4
=6+ 8/(x-4) +(x-4)
≥6+4√2
当且仅当8/(x-4) =(x-4)时,等号成立
∴最小值为：6+4√2