2x+8y-xy=0
2x+8y=xy
2/y+8/x=1
x+y
=(x+y)*1
=(x+y)(2/y + 8/x)
=8+2+ 2x/y +8y/x
≥10+2√[(2x/y)(8y/x)]
=10+2√16=18
最小值为18