已知:{x^2-y^2=16,x+y=2;求(3x-3y)/(y^2-x^2)+(x^2-2xy+y^2)/(x^2-y^2)-(x^2-x-6)/(x+2)÷(x+y)的值
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(x+y)(x-y)=16
x+y=2
所以x-y=8
相加
2x=10
x=5
原式=-3(x-y)/(x+y)(x-y)+(x+y)²/(x+y)(x-y)-(x-3)(x+2)/(x+2)(x+y)
=-3/(x+y)+(x+y)/(x-y)-(x-3)/(x+y)
=-3/2+2/8-2/2
=-9/4
x+y=2
所以x-y=8
相加
2x=10
x=5
原式=-3(x-y)/(x+y)(x-y)+(x+y)²/(x+y)(x-y)-(x-3)(x+2)/(x+2)(x+y)
=-3/(x+y)+(x+y)/(x-y)-(x-3)/(x+y)
=-3/2+2/8-2/2
=-9/4
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