已知2x平方-xy-3y平方=0,且x不等于-y,求x比上y-（x-y）分之x平方

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2x²-xy-3y²=0
(x+y)(2x-3y)=0
x=-y(舍去)或x=3y/2
x/y=3/2
x/y-x²/(x-y)
=x/y-x²/(x²-2xy+y²)
=x/y-(x/y)²/[(x/y)²-2(x/y)+1]
=(3/2)-(3/2)²/[(3/2)²-2(3/2)+1]
=-15/2