y=2/(x+1)
令a=x+y
=x+2/(x+1)
=(x+1)+2/(x+1)-1
且x+1>1
(x+1)+2/(x+1)可以看做对勾函数
则x+1=√(2/1)=√2时最小=2√2
所以x=√2-1,y=√2,x+y最小=2√2-1