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问题: ∫[1/(9-x^2)]*dx如何求

解答:

∫[1/(9-x^2)]*dx
=∫{1/[(3-x)*(3+x)]}dx
=(1/6)∫{[1/(3-x)]+[1/(3+x)]}dx
=(1/6){∫[1/(3-x)]dx+∫[1/(3+x)]dx}
=(1/6)[-ln(3-x)+ln(3+x)]
=(1/6)ln[(3+x)/(3-x)]