已知x/y=2/7,求分式x²-3xy+2y²/x²-2xy+y²的值.

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x/y=2/7
y=7/2x

x²-3xy+2y²/x²-2xy+y²
=(x-y)²-xy/(x-y)²
=[(x-7/2x)-x*7/2x] /(x-7/2x)²
=(25/4x²-7/2x²)/(25/4x²)
=(11/4x²)/(25/4x²)
=11/25