[(2x+y)^2-(2x-y)(2x+y)]÷2y-1/2y
=（4x^2+4xy+y^2-4x^2+y^2)÷2y-1/2y
=（4xy+2y^2）÷2y-1/2y
=2x+y-1/2y
=2x+1/2y