已知x/y=2/7,求分式(x2-3xy+2y2)/(x2-2xy+y2)的值

已知x/y=2/7,求分式(x2-3xy+2y2)/(x2-2xy+y2)的值
已知x/y=2/7,求分式(x2-3xy+2y2)/(x2-2xy+y2)的值

已知x/y=2/7,求分式(x2-3xy+2y2)/(x2-2xy+y2)的值
x/y=2/7
x=2y/7
(x2-3xy+2y2)/(x2-2xy+y2)
=（x-2y)(x-y)/(x-y)²
=（x-2y)/(x-y)
=(2y/7-2y)/(2y/7-y)
=12/5

已知X/Y=2/7，得知X=2/7*Y，分式X用Y代替得最终值12/5