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积分∫(2r)/{(x^2+r^2)^(3/2)}dr求完全具体步骤!∫(

题目

积分∫(2r)/{(x^2+r^2)^(3/2)} dr
求完全具体步骤!
∫(2r)/{(x^2+r^2)^(3/2)} dr
=∫(x^2+r^2)^(-3/2) dr^2
为啥?

优质解答

∫(2r)/{(x^2+r^2)^(3/2)} dr
=∫(x^2+r^2)^(-3/2) dr^2
=∫(x^2+r^2)^(-3/2) d(x^2+r^2)
=(x^2+r^2)^(-3/2+1)/(-3/2+1)+C
=-2(x^2+r^2)^(-1/2)+C
=-2/√(x^2+r^2)+C

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