x² /(x²-2xy) : [(2xy /(x²-4y²) -y/( x+2y)]=
=x²/x(x-2y) : [(2xy /(x-2y)(x+2y) -y/( x+2y)]=
=x/(x-2y) : [(2xy -y(x-2y)/(x-2y)(x+2y)]=
=x/(x-2y) : [(2xy -xy+2y²)/(x-2y)(x+2y)]=
=x/(x-2y) : y(x+2y)/(x-2y)(x+2y)=
=x/(x-2y) : y/(x-2y)=
=x/(x-2y) × (x-2y)/y= x/y