已知x/y=4/3,求3x²-5xy+2y²/2x²+3xy-5y²的值

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x/y=4/3,
设比的每一份为t,
则x=4t,y=3t
所以
（3x²-5xy+2y²）/(2x²+3xy-5y²)
=(48t²-60t²+18t²)/(32t²+36t²-45t²)
=6t²/(23t²)
=6/23