x/y=2/3
所以y=3x/2
原式=[5y²-(x-2y)(x+2y)]/(x-2y)÷(x-3y)²/(x-2y)
=(9y²-x²)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)(x-3y)/(x-2y)*(x-2y)/(x-3y)²
=-(x+3y)/(x-3y)
=-(x+3x/2)/(x-3x/2)
=5
已知x/y=2/3求[5y^2/(x-2y)-x-2y]÷（x^2-6xy+9y^2）/(x-2y）的值
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