已知/a+1/2/+根号b-3=0,化简代数式后求值：[(2a+b)^2-(b+2a)(2a-b)-6b]/2b

a+1/2=0
b-3=0
∴a=-1/2
b=3
[(2a+b)^2-(b+2a)(2a-b)-6b]/2b
=[(2a+b)(2a+b-2a+b)-6b]/2b
=2a+b-3
=-1+3-3
=-1