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f(x)=1/(x²+ 5x+4)=1/(x+1)(x+4)
=1/3 [1/(x+1)-1/(x+4)]
=1/3 [1/(x-1+2) -1/(x-1+5)]
=1/6 1/[1+(x-1)/2] -1/15 1/[1+(x-1)/5]
=1/6 ∑(n=0:∞)(-1)^n[(x-1)/2] ^n -1/15 ∑(n=0:∞)(-1)^n[(x-1)/5] ^n
=1/3 ∑(n=0:∞)[1/2^(n+1)-1/5^(n+1)](-1)^n (x-1)^n
由-1<(x-1)/2 <1,-1<(x-1)/5<1得,-1<x<3
=1/3 [1/(x+1)-1/(x+4)]
=1/3 [1/(x-1+2) -1/(x-1+5)]
=1/6 1/[1+(x-1)/2] -1/15 1/[1+(x-1)/5]
=1/6 ∑(n=0:∞)(-1)^n[(x-1)/2] ^n -1/15 ∑(n=0:∞)(-1)^n[(x-1)/5] ^n
=1/3 ∑(n=0:∞)[1/2^(n+1)-1/5^(n+1)](-1)^n (x-1)^n
由-1<(x-1)/2 <1,-1<(x-1)/5<1得,-1<x<3
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