已知x-3y=0,求(x²-2xy+y²/x-y)-2y的值

已知x-3y=0,求(x²-2xy+y²/x-y)-2y的值
已知x-3y=0,求(x²-2xy+y²/x-y)-2y的值

已知x-3y=0,求(x²-2xy+y²/x-y)-2y的值
(x²－2xy＋y²)/(x－y)－2y
=[(x－y)²/(x－y)]－2y
=(x－y)－2y
=x－3y
=0

(x²-2xy+y²/x-y)-2y
=（x-y）²/（x-y）-2y
=x-y-2y
=x-3y
=0

(x²-2xy+y²/x-y)-2y 通分，得
(x²-2xy+y²-2xy+2y²)/(x-y)
=(x²-4xy+3y²)/(x-y)
=(x-y)(x-3y)/(x-y)
=x-3y
由题知 x-3y=0