3a+ 1/2x =2x-a的解为2,
则:3a+1/2*2=2*2-a
3a+1=4-a
4a=3
a=3/4
(8a^2- 1/2)/a
=8a-1/(2a)
=8*3/4-1/(2*3/4)
=6-1/(3/2)
=6-2/3
=16/3