求ln(x)/x關於x-1的幂級數展開式

求ln(x)/x關於x-1的幂級數展開式

lnx=ln(x-1+1)=(x-1)-(x-1)^2/2+(x-1)^3/3-.
1/x=1/(1+x-1)=1-(x-1)+(x-1)^2-(x-1)^3+.
設ln(x)/x=a0+a1(x-1)+a2(x-1)^2+a3(x-1)^3+.
[(x-1)-(x-1)^2/2+(x-1)^3/3-.]
=[a0+a1(x-1)+a2(x-1)^2+a3(x-1)^3+.][1-(x-1)+(x-1)^2-(x-1)^3+.]
比較係數得:a0=0,a1-a0=1,a2+a0-a1=-1/2,.
ln(x)/x=(x-1)+(x-1)^2/2+.