[(x+2y）²-（x+y）（x-y）-4y²]÷2y =[x^2+4xy+4y^2-(x^2-y^2)-4y^2]÷2y
=[x^2+4xy+4y^2-x^2+y^2-4y^2]÷2y
=[4xy+y^2]÷2y
=2x+y/2