求(3x^2+9x+7)/(x+1)-(2x^2+5x-3)/(x-1)-(x^3+x-1)/(x^2-1)的值
问题描述：
求(3x^2+9x+7)/(x+1)-(2x^2+5x-3)/(x-1)-(x^3+x-1)/(x^2-1)的值
答
(3x^2+9x+7)/(x+1)-(2x^2+5x-3)/(x-1)-(x^3+x-1)/(x^2-1)
=[(3x²+9x+7)(x-1)-(2x²+5x-3)(x+1)-(x³+x-1)]/(x²-1)
=[3x³-3x²+9x²-9x+7x-7-(2x³+2x²+5x²+5x-3x-3)-(x³+x-1)]/(x²-1)
=(3x³+6x²-2x-7-2x³-7x²-2x+3-x³-x+1)/(x²-1)
=(-x²-5x-3)/(x²-1)
=-(x²+5x+3)/(x²-1)
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