速求!在线等!已知x-2y=0,求x方-y方分之y除以x-y分之1的值.在线等!

题目

速求!在线等!已知x-2y=0,求x方-y方分之y除以x-y分之1的值.在线等!

答案

x-2y=0
x=2y
y/(x^2-y^2)÷1/(x-y)
=y/(x^2-y^2)*(x-y)
=y/[(x-y)(x+y)]*(x-y)
=y/(x+y)
=y/(2y+y)
=y/(3y)
=1/3