求不定积分1/x^2(2x^2-2x+1)^2
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你是不是想求:∫{1/[x^2(2x^2-2x+1)^2]}dx
? 若是这样,则方法如下:
令1/x=u,则x=1/u, ∴dx=-(1/u^2)du。
∴原式=∫{1/[(1/u^2)(2/u^2-2/u+1)^2]}[-(1/u^2)]du
=-∫[u^2/(2-2u+u^2)^2]du
=-∫[(u^2-2u+2+2u-2)/(u^2-2u+2)^2]du
=-∫[1/(u^2-2u+2)]du+2∫[(u-1)/(u^2-2u+2)^2]du
=-∫{1/[(u-1)^2+1]}d(u-1)+2∫{(u-1)/[(u-1)^2+1]}d(u-1)
=-arctan(u-1)+∫{1/[(u-1)^2+1]}d(u-1)^2
=-arctan(1/x-1)+ln|(u-1)^2+1|+C
=-arctan(1/x-1)+ln|(1/x-1)^2+1|+C
? 若是这样,则方法如下:
令1/x=u,则x=1/u, ∴dx=-(1/u^2)du。
∴原式=∫{1/[(1/u^2)(2/u^2-2/u+1)^2]}[-(1/u^2)]du
=-∫[u^2/(2-2u+u^2)^2]du
=-∫[(u^2-2u+2+2u-2)/(u^2-2u+2)^2]du
=-∫[1/(u^2-2u+2)]du+2∫[(u-1)/(u^2-2u+2)^2]du
=-∫{1/[(u-1)^2+1]}d(u-1)+2∫{(u-1)/[(u-1)^2+1]}d(u-1)
=-arctan(u-1)+∫{1/[(u-1)^2+1]}d(u-1)^2
=-arctan(1/x-1)+ln|(u-1)^2+1|+C
=-arctan(1/x-1)+ln|(1/x-1)^2+1|+C
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