a=√[(2x+2)/(x+2)]
则a-1/a=7/12
两边乘12a
12a^2-7a-12=0
(3a-4)(4a+3)=0
a=√[(2x+2)/(x+2)]>0
所以a=√[(2x+2)/(x+2)]=4/3
(2x+2)/(x+2)=16/9
16x+32=18x+18
x=7