解【(x+2y)的平方-(x+y)(x-y)-5y方】÷(2x )
=[x^2+4xy+4y^2-(x^2-y^2)-5y^2]÷(2x )
=[x^2+4xy+4y^2-x^2+y^2-5y^2]÷(2x )
=[x^2+4xy-x^2]÷(2x )
=[4xy]÷(2x )
=2y
=2×1/2
=1