已知x/y=2/7,则x2-3xy+2y2/2x2-3xy+7y2的值是多少?

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已知x/y=2/7,则x2-3xy+2y2/2x2-3xy+7y2的值是多少?已知x/y=2/7,则x2-3xy+2y2/2x2-3xy+7y2的值是多少?已知x/y=2/7,则x2-3xy+2y2/

已知x/y=2/7,则x2-3xy+2y2/2x2-3xy+7y2的值是多少?
已知x/y=2/7,则x2-3xy+2y2/2x2-3xy+7y2的值是多少?

已知x/y=2/7,则x2-3xy+2y2/2x2-3xy+7y2的值是多少?
设x=2t,y=7t
(x²-3xy+2y²)/(2x²-3xy+7y²)=(x-2y)(x-y)/(2x²-3xy+7y²)=(2t-14t)(2t-7t)/(8t²-42t²+343t²)=60t²/309t²=20/103