把函数f(x)=(1-x)ln(1+x)展开成x的幂函数

如题所述

第1个回答  2014-12-16
1/(1+x) = ∑<n=0,∞> (-1)^nx^n (-1<x<1)
ln(1+x) =∫<0,x>dt/(1+t) = ∑<n=0,∞> (-1)^nx^(n +1)/(n+1) (-1<x≤1)
(1-x)ln(1+x) =ln(1+x)-xln(1+x)
= ∑<n=0,∞> (-1)^nx^(n +1)/(n+1) - x∑<n=0,∞> (-1)^nx^(n +1)/(n+1)
= ∑<n=0,∞> (-1)^n [x^(n +1)-x^(n+2)]/(n+1) (-1<x≤1)本回答被网友采纳
第2个回答  2014-12-16
x/Log[2]-(3 x^2)/(2 Log[2])+(5 x^3)/(6 Log[2])-(7 x^4)/(12 Log[2])+(9 x^5)/(20 Log[2])-(11 x^6)/(30 Log[2])+(13 x^7)/(42 Log[2])-(15 x^8)/(56 Log[2])+(17 x^9)/(72 Log[2])-(19 x^10)/(90 Log[2])+O[x]^11 Rational[-19, 90]/Log[2]}, 1, 11, 1]