已知y⼀x-x⼀y=-5,求分式3x^2+xy-3y^2⼀2x^2-xy-2y^2的值

2024-12-18 02:04:40
推荐回答(3个)
回答1:

y/x-x/y=-5,
两边乘xy得
y^2-x^2=-5xy
(3x^2+xy-3y^2)/(2x^2-xy-2y^2)
=(15xy+xy)/(10xy-xy)
=16/9

回答2:

y/x-x/y=5,
同乘xy得,
xy=(y²-x²)/(-5),
原式=[(-15x²+y²-x²+15y²)/(-5)]/[(-10x²-y²+x²+10y²)/(-5)
=[16(y²-x²)]/[9(y²-x²)]
=16/9

回答3:

16/9