已知5x-4y=0且xy不等于0,求x^2+y^2/x^2-y^2-x+y/x-y的值

已知5x-4y=0且xy不等于0,求x^2+y^2/x^2-y^2-x+y/x-y的值
已知5x-4y=0且xy不等于0,求x^2+y^2/x^2-y^2-x+y/x-y的值

已知5x-4y=0且xy不等于0,求x^2+y^2/x^2-y^2-x+y/x-y的值
5x-4y=0;
x=4y/5;
x^2+y^2/x^2-y^2-x+y/x-y
=（x²+y²-(x+y)²）/(x²-y²)
=(x²+y²-x²-y²-2xy)/(x²-y²)
=-2xy/(x²-y²)
=-2y×(4y/5)/(16y²/25-y²)
=-8y²/5/-9y²/25
=40/9;
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题目是这个意思吗？
x^2+（y^2/x^2）-y^2-x+（y/x）-y
= -9x^2/16-9x/4+45/16