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4x^3-x^2-11x-6 = (x+1)(4x^2-5x-6) = (x+1)(4x+3)(x-2)
设 (4x^2+9x-1)/(4x^3-x^2-11x-6) = a/(x+1) + b/(x-2) + c/(4x+3), 通分,
分子 = a(4x^2-5x-6) + b(x+1)(4x+3) + c(x+1)(x-2) = 4x^2+9x-1
4a+4b+c = 4, -5a+7b-c = 9, -6a+3b-2c = -1,
联立解得 a = -2, b = 1, c = 8.
I = -2∫dx/(x+1) + ∫dx/(x-2) + 8∫dx/(4x+3)
= -2ln|x+1| + ln|x-2| + 2ln|4x+3| + C
= ln[|x+2|(4x+3)^2/(x+1)^2] + C
设 (4x^2+9x-1)/(4x^3-x^2-11x-6) = a/(x+1) + b/(x-2) + c/(4x+3), 通分,
分子 = a(4x^2-5x-6) + b(x+1)(4x+3) + c(x+1)(x-2) = 4x^2+9x-1
4a+4b+c = 4, -5a+7b-c = 9, -6a+3b-2c = -1,
联立解得 a = -2, b = 1, c = 8.
I = -2∫dx/(x+1) + ∫dx/(x-2) + 8∫dx/(4x+3)
= -2ln|x+1| + ln|x-2| + 2ln|4x+3| + C
= ln[|x+2|(4x+3)^2/(x+1)^2] + C
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