展开f(x) = ln(1+x)得f(x) = x-(x^2)/2+(x^3)/3-(x^4)/4+...+((-1)^r+1)(x^r)/r+...则展开f(x) = ln(1+x)x^2得f(x) = x^2(x-(x^2)/2+(x^3)/3-(x^4)/4+...+((-1)^r+1)(x^r)/r+...)f(x) = x^3-(x^4)/2+(x^5)/3-(x^6)/4+..+((-1)^r+1)(x^(r+2))/r+...