√[2x/(x+2）] - √（1/x+1/2）=5/6
√[2x/(x+2）] - √[（x+2)/2x]=5/6
设√[2x/(x+2）] =A A>>0
原题：
A-1/A=5/6
6A^2-6=5A
6A^2-5A-6=0
(3A+2)(2A-3)=0
3A+2=0 A=-2/3(舍)