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
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
16/9