八年级数学 化简:1/(x+3)-6/(x²-9)-(x-1)/(6+2x)

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1/(x+3)-6/(x²-9)-(x-1)/(6+2x)
=1/(x+3)-6/(x-3)(x+3)-(x-1)/2(x+3)
=2(x-3)/2(x-3)(x+3)-12/2(x-3)(x+3)-(x-1)(x-3)/2(x-3)(x+3)
=[2(x-3)-12-(x-1)(x-3)]/2(x-3)(x+3)
=[2x-6-12-x^2+4x-3]/2(x-3)(x+3)
=(-x^2+6x-21)/2(x-3)(x+3)
=-(x^2-6x+21)/2(x-3)(x+3).
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