先分解为部分分式,再展开
f(x)=1/[(2x-1)(x-1)]
=1/(x-1)-2/(2x-1)
=-1/(1-x)+2/(1-2x)
=-[1+x+x^2+x^3+.+x^n+..]+2[1+2x+4x^2+8x^3+...+2^nx^n+..]
=1+3x+7x^2+15x^3+...+(2^(n+1)-1)x^n+..