∫(1到正无穷大)dx/{x^2(x+1)}

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∫(1到正无穷大)dx/{x^2(x+1)}

∫(1到正无穷大)dx/{x^2(x+1)}
∫(1到正无穷大)dx/{x^2(x+1)}

∫(1到正无穷大)dx/{x^2(x+1)}
let
1/[x^2(x+1)] = A/x^2+B/x+C/(x+1)
=> 1=A(x+1) +Bx(x+1)+Cx^2
put x=-1
C = 1
coef. of x^2
B +C =0
B= -1
coef. of constant
A=1
1/[x^2(x+1)] = 1/x^2-1/x+1/(x+1)
∫(1到正无穷大)dx/{x^2(x+1)}
=∫(1到正无穷大)[ 1/x^2-1/x+1/(x+1)] dx
= [-1/x -lnx + ln(x+1)] (1到正无穷大)
= 1-ln2

1/x²(x+1)=(Ax+B)/x²+C/(x+1)
(Ax+B)(x+1)+Cx²=1
Ax²+Ax+Bx+B+Cx²=1
(A+C)x²+(A+B)x+B=1
A+C=0
A+B=0
B=1
A=-1
C=1
1/x²(x+1)= (-x+1)/x&#...

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1/x²(x+1)=(Ax+B)/x²+C/(x+1)
(Ax+B)(x+1)+Cx²=1
Ax²+Ax+Bx+B+Cx²=1
(A+C)x²+(A+B)x+B=1
A+C=0
A+B=0
B=1
A=-1
C=1
1/x²(x+1)= (-x+1)/x²+1/(x+1)
∫(1-->+∝)dx/{x²(x+1)}
=∫(1-->+∝)[(-x+1)/x²+1/(x+1)]dx
=∫(1-->+∝)[-1/x+1/x²+1/(x+1)]dx
=-lnx-1/x+ln(1+x) 1-->+∝
=-1/x+ln(1+x)/x
=1-ln2

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上面两个的做法对