原式=[(x²+y²)(x+y)(x-y)/(2x-y)(x+y)]×[(2x-y)/y(x-y)]÷[(x²+y²)²/4]
=[(x²+y²)(x-y)/(2x-y)]×[(2x-y)/y(x-y)]×[4/(x²+y²)²]
=4(x²+y²)(x-y)(2x-y)/[(2x-y)y(x-y)(x²+y²)²]
=4/[y(x²+y²)]