y=2x/(x+1) =(2x+2-2)/(x+1) =(2x+2)/(x+1)-2/(x+1) =2-2/(x+1)因为2/(x+1)≠0，所以2-2/(x+1)≠2即y≠2，也即值域为(-∞，2)∪(2，+∞)
不等于2
