若x/y=2/7则7x²-3xy+2y²/2x²-3xy+7y²=x 2 7x²-3xy+2y²__= __ _____________ =y 7 2x²-3xy+7y²

若x/y=2/7则7x²-3xy+2y²/2x²-3xy+7y²=x 2 7x²-3xy+2y²__= __ _____________ =y 7 2x²-3xy+7y²
若x/y=2/7则7x²-3xy+2y²/2x²-3xy+7y²=
x 2 7x²-3xy+2y²
__= __ _____________ =
y 7 2x²-3xy+7y²

若x/y=2/7则7x²-3xy+2y²/2x²-3xy+7y²=x 2 7x²-3xy+2y²__= __ _____________ =y 7 2x²-3xy+7y²
28/103
7x=2y,原式=(7x*x-3xy+2y*y)/(2x*x-3xy+7y*y)
=(2xy-3xy+7xy)/(4/7*xy-3xy+49/2*xy)
=28/103

等于28/103

28/103